/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com * Copyright (c) 2016 Facebook * * This program is free software; you can redistribute it and/or * modify it under the terms of version 2 of the GNU General Public * License as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. */ #include #include #include #include #include #include #include #include #include #include /* bpf_check() is a static code analyzer that walks eBPF program * instruction by instruction and updates register/stack state. * All paths of conditional branches are analyzed until 'bpf_exit' insn. * * The first pass is depth-first-search to check that the program is a DAG. * It rejects the following programs: * - larger than BPF_MAXINSNS insns * - if loop is present (detected via back-edge) * - unreachable insns exist (shouldn't be a forest. program = one function) * - out of bounds or malformed jumps * The second pass is all possible path descent from the 1st insn. * Since it's analyzing all pathes through the program, the length of the * analysis is limited to 64k insn, which may be hit even if total number of * insn is less then 4K, but there are too many branches that change stack/regs. * Number of 'branches to be analyzed' is limited to 1k * * On entry to each instruction, each register has a type, and the instruction * changes the types of the registers depending on instruction semantics. * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is * copied to R1. * * All registers are 64-bit. * R0 - return register * R1-R5 argument passing registers * R6-R9 callee saved registers * R10 - frame pointer read-only * * At the start of BPF program the register R1 contains a pointer to bpf_context * and has type PTR_TO_CTX. * * Verifier tracks arithmetic operations on pointers in case: * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), * 1st insn copies R10 (which has FRAME_PTR) type into R1 * and 2nd arithmetic instruction is pattern matched to recognize * that it wants to construct a pointer to some element within stack. * So after 2nd insn, the register R1 has type PTR_TO_STACK * (and -20 constant is saved for further stack bounds checking). * Meaning that this reg is a pointer to stack plus known immediate constant. * * Most of the time the registers have UNKNOWN_VALUE type, which * means the register has some value, but it's not a valid pointer. * (like pointer plus pointer becomes UNKNOWN_VALUE type) * * When verifier sees load or store instructions the type of base register * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer * types recognized by check_mem_access() function. * * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' * and the range of [ptr, ptr + map's value_size) is accessible. * * registers used to pass values to function calls are checked against * function argument constraints. * * ARG_PTR_TO_MAP_KEY is one of such argument constraints. * It means that the register type passed to this function must be * PTR_TO_STACK and it will be used inside the function as * 'pointer to map element key' * * For example the argument constraints for bpf_map_lookup_elem(): * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, * .arg1_type = ARG_CONST_MAP_PTR, * .arg2_type = ARG_PTR_TO_MAP_KEY, * * ret_type says that this function returns 'pointer to map elem value or null' * function expects 1st argument to be a const pointer to 'struct bpf_map' and * 2nd argument should be a pointer to stack, which will be used inside * the helper function as a pointer to map element key. * * On the kernel side the helper function looks like: * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) * { * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; * void *key = (void *) (unsigned long) r2; * void *value; * * here kernel can access 'key' and 'map' pointers safely, knowing that * [key, key + map->key_size) bytes are valid and were initialized on * the stack of eBPF program. * } * * Corresponding eBPF program may look like: * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), * here verifier looks at prototype of map_lookup_elem() and sees: * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, * Now verifier knows that this map has key of R1->map_ptr->key_size bytes * * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, * Now verifier checks that [R2, R2 + map's key_size) are within stack limits * and were initialized prior to this call. * If it's ok, then verifier allows this BPF_CALL insn and looks at * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function * returns ether pointer to map value or NULL. * * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' * insn, the register holding that pointer in the true branch changes state to * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false * branch. See check_cond_jmp_op(). * * After the call R0 is set to return type of the function and registers R1-R5 * are set to NOT_INIT to indicate that they are no longer readable. */ /* verifier_state + insn_idx are pushed to stack when branch is encountered */ struct bpf_verifier_stack_elem { /* verifer state is 'st' * before processing instruction 'insn_idx' * and after processing instruction 'prev_insn_idx' */ struct bpf_verifier_state st; int insn_idx; int prev_insn_idx; struct bpf_verifier_stack_elem *next; }; #define BPF_COMPLEXITY_LIMIT_INSNS 98304 #define BPF_COMPLEXITY_LIMIT_STACK 1024 #define BPF_MAP_PTR_POISON ((void *)0xeB9F + POISON_POINTER_DELTA) struct bpf_call_arg_meta { struct bpf_map *map_ptr; bool raw_mode; bool pkt_access; int regno; int access_size; }; /* verbose verifier prints what it's seeing * bpf_check() is called under lock, so no race to access these global vars */ static u32 log_level, log_size, log_len; static char *log_buf; static DEFINE_MUTEX(bpf_verifier_lock); /* log_level controls verbosity level of eBPF verifier. * verbose() is used to dump the verification trace to the log, so the user * can figure out what's wrong with the program */ static __printf(1, 2) void verbose(const char *fmt, ...) { va_list args; if (log_level == 0 || log_len >= log_size - 1) return; va_start(args, fmt); log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); va_end(args); } /* string representation of 'enum bpf_reg_type' */ static const char * const reg_type_str[] = { [NOT_INIT] = "?", [UNKNOWN_VALUE] = "inv", [PTR_TO_CTX] = "ctx", [CONST_PTR_TO_MAP] = "map_ptr", [PTR_TO_MAP_VALUE] = "map_value", [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", [PTR_TO_MAP_VALUE_ADJ] = "map_value_adj", [FRAME_PTR] = "fp", [PTR_TO_STACK] = "fp", [CONST_IMM] = "imm", [PTR_TO_PACKET] = "pkt", [PTR_TO_PACKET_END] = "pkt_end", }; #define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x) static const char * const func_id_str[] = { __BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN) }; #undef __BPF_FUNC_STR_FN static const char *func_id_name(int id) { BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID); if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id]) return func_id_str[id]; else return "unknown"; } static void print_verifier_state(struct bpf_verifier_state *state) { struct bpf_reg_state *reg; enum bpf_reg_type t; int i; for (i = 0; i < MAX_BPF_REG; i++) { reg = &state->regs[i]; t = reg->type; if (t == NOT_INIT) continue; verbose(" R%d=%s", i, reg_type_str[t]); if (t == CONST_IMM || t == PTR_TO_STACK) verbose("%lld", reg->imm); else if (t == PTR_TO_PACKET) verbose("(id=%d,off=%d,r=%d)", reg->id, reg->off, reg->range); else if (t == UNKNOWN_VALUE && reg->imm) verbose("%lld", reg->imm); else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || t == PTR_TO_MAP_VALUE_OR_NULL || t == PTR_TO_MAP_VALUE_ADJ) verbose("(ks=%d,vs=%d,id=%u)", reg->map_ptr->key_size, reg->map_ptr->value_size, reg->id); if (reg->min_value != BPF_REGISTER_MIN_RANGE) verbose(",min_value=%lld", (long long)reg->min_value); if (reg->max_value != BPF_REGISTER_MAX_RANGE) verbose(",max_value=%llu", (unsigned long long)reg->max_value); if (reg->min_align) verbose(",min_align=%u", reg->min_align); if (reg->aux_off) verbose(",aux_off=%u", reg->aux_off); if (reg->aux_off_align) verbose(",aux_off_align=%u", reg->aux_off_align); } for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { if (state->stack_slot_type[i] == STACK_SPILL) verbose(" fp%d=%s", -MAX_BPF_STACK + i, reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]); } verbose("\n"); } static const char *const bpf_class_string[] = { [BPF_LD] = "ld", [BPF_LDX] = "ldx", [BPF_ST] = "st", [BPF_STX] = "stx", [BPF_ALU] = "alu", [BPF_JMP] = "jmp", [BPF_RET] = "BUG", [BPF_ALU64] = "alu64", }; static const char *const bpf_alu_string[16] = { [BPF_ADD >> 4] = "+=", [BPF_SUB >> 4] = "-=", [BPF_MUL >> 4] = "*=", [BPF_DIV >> 4] = "/=", [BPF_OR >> 4] = "|=", [BPF_AND >> 4] = "&=", [BPF_LSH >> 4] = "<<=", [BPF_RSH >> 4] = ">>=", [BPF_NEG >> 4] = "neg", [BPF_MOD >> 4] = "%=", [BPF_XOR >> 4] = "^=", [BPF_MOV >> 4] = "=", [BPF_ARSH >> 4] = "s>>=", [BPF_END >> 4] = "endian", }; static const char *const bpf_ldst_string[] = { [BPF_W >> 3] = "u32", [BPF_H >> 3] = "u16", [BPF_B >> 3] = "u8", [BPF_DW >> 3] = "u64", }; static const char *const bpf_jmp_string[16] = { [BPF_JA >> 4] = "jmp", [BPF_JEQ >> 4] = "==", [BPF_JGT >> 4] = ">", [BPF_JGE >> 4] = ">=", [BPF_JSET >> 4] = "&", [BPF_JNE >> 4] = "!=", [BPF_JSGT >> 4] = "s>", [BPF_JSGE >> 4] = "s>=", [BPF_CALL >> 4] = "call", [BPF_EXIT >> 4] = "exit", }; static void print_bpf_insn(const struct bpf_verifier_env *env, const struct bpf_insn *insn) { u8 class = BPF_CLASS(insn->code); if (class == BPF_ALU || class == BPF_ALU64) { if (BPF_SRC(insn->code) == BPF_X) verbose("(%02x) %sr%d %s %sr%d\n", insn->code, class == BPF_ALU ? "(u32) " : "", insn->dst_reg, bpf_alu_string[BPF_OP(insn->code) >> 4], class == BPF_ALU ? "(u32) " : "", insn->src_reg); else verbose("(%02x) %sr%d %s %s%d\n", insn->code, class == BPF_ALU ? "(u32) " : "", insn->dst_reg, bpf_alu_string[BPF_OP(insn->code) >> 4], class == BPF_ALU ? "(u32) " : "", insn->imm); } else if (class == BPF_STX) { if (BPF_MODE(insn->code) == BPF_MEM) verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", insn->code, bpf_ldst_string[BPF_SIZE(insn->code) >> 3], insn->dst_reg, insn->off, insn->src_reg); else if (BPF_MODE(insn->code) == BPF_XADD) verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", insn->code, bpf_ldst_string[BPF_SIZE(insn->code) >> 3], insn->dst_reg, insn->off, insn->src_reg); else verbose("BUG_%02x\n", insn->code); } else if (class == BPF_ST) { if (BPF_MODE(insn->code) != BPF_MEM) { verbose("BUG_st_%02x\n", insn->code); return; } verbose("(%02x) *(%s *)(r%d %+d) = %d\n", insn->code, bpf_ldst_string[BPF_SIZE(insn->code) >> 3], insn->dst_reg, insn->off, insn->imm); } else if (class == BPF_LDX) { if (BPF_MODE(insn->code) != BPF_MEM) { verbose("BUG_ldx_%02x\n", insn->code); return; } verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", insn->code, insn->dst_reg, bpf_ldst_string[BPF_SIZE(insn->code) >> 3], insn->src_reg, insn->off); } else if (class == BPF_LD) { if (BPF_MODE(insn->code) == BPF_ABS) { verbose("(%02x) r0 = *(%s *)skb[%d]\n", insn->code, bpf_ldst_string[BPF_SIZE(insn->code) >> 3], insn->imm); } else if (BPF_MODE(insn->code) == BPF_IND) { verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", insn->code, bpf_ldst_string[BPF_SIZE(insn->code) >> 3], insn->src_reg, insn->imm); } else if (BPF_MODE(insn->code) == BPF_IMM && BPF_SIZE(insn->code) == BPF_DW) { /* At this point, we already made sure that the second * part of the ldimm64 insn is accessible. */ u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; bool map_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD; if (map_ptr && !env->allow_ptr_leaks) imm = 0; verbose("(%02x) r%d = 0x%llx\n", insn->code, insn->dst_reg, (unsigned long long)imm); } else { verbose("BUG_ld_%02x\n", insn->code); return; } } else if (class == BPF_JMP) { u8 opcode = BPF_OP(insn->code); if (opcode == BPF_CALL) { verbose("(%02x) call %s#%d\n", insn->code, func_id_name(insn->imm), insn->imm); } else if (insn->code == (BPF_JMP | BPF_JA)) { verbose("(%02x) goto pc%+d\n", insn->code, insn->off); } else if (insn->code == (BPF_JMP | BPF_EXIT)) { verbose("(%02x) exit\n", insn->code); } else if (BPF_SRC(insn->code) == BPF_X) { verbose("(%02x) if r%d %s r%d goto pc%+d\n", insn->code, insn->dst_reg, bpf_jmp_string[BPF_OP(insn->code) >> 4], insn->src_reg, insn->off); } else { verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", insn->code, insn->dst_reg, bpf_jmp_string[BPF_OP(insn->code) >> 4], insn->imm, insn->off); } } else { verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); } } static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx) { struct bpf_verifier_stack_elem *elem; int insn_idx; if (env->head == NULL) return -1; memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); insn_idx = env->head->insn_idx; if (prev_insn_idx) *prev_insn_idx = env->head->prev_insn_idx; elem = env->head->next; kfree(env->head); env->head = elem; env->stack_size--; return insn_idx; } static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx) { struct bpf_verifier_stack_elem *elem; elem = kmalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL); if (!elem) goto err; memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); elem->insn_idx = insn_idx; elem->prev_insn_idx = prev_insn_idx; elem->next = env->head; env->head = elem; env->stack_size++; if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { verbose("BPF program is too complex\n"); goto err; } return &elem->st; err: /* pop all elements and return */ while (pop_stack(env, NULL) >= 0); return NULL; } #define CALLER_SAVED_REGS 6 static const int caller_saved[CALLER_SAVED_REGS] = { BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 }; static void init_reg_state(struct bpf_reg_state *regs) { int i; for (i = 0; i < MAX_BPF_REG; i++) { regs[i].type = NOT_INIT; regs[i].imm = 0; regs[i].min_value = BPF_REGISTER_MIN_RANGE; regs[i].max_value = BPF_REGISTER_MAX_RANGE; regs[i].min_align = 0; regs[i].aux_off = 0; regs[i].aux_off_align = 0; } /* frame pointer */ regs[BPF_REG_FP].type = FRAME_PTR; /* 1st arg to a function */ regs[BPF_REG_1].type = PTR_TO_CTX; } static void __mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno) { regs[regno].type = UNKNOWN_VALUE; regs[regno].id = 0; regs[regno].imm = 0; } static void mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno) { BUG_ON(regno >= MAX_BPF_REG); __mark_reg_unknown_value(regs, regno); } static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno) { regs[regno].min_value = BPF_REGISTER_MIN_RANGE; regs[regno].max_value = BPF_REGISTER_MAX_RANGE; regs[regno].min_align = 0; } static void mark_reg_unknown_value_and_range(struct bpf_reg_state *regs, u32 regno) { mark_reg_unknown_value(regs, regno); reset_reg_range_values(regs, regno); } enum reg_arg_type { SRC_OP, /* register is used as source operand */ DST_OP, /* register is used as destination operand */ DST_OP_NO_MARK /* same as above, check only, don't mark */ }; static int check_reg_arg(struct bpf_reg_state *regs, u32 regno, enum reg_arg_type t) { if (regno >= MAX_BPF_REG) { verbose("R%d is invalid\n", regno); return -EINVAL; } if (t == SRC_OP) { /* check whether register used as source operand can be read */ if (regs[regno].type == NOT_INIT) { verbose("R%d !read_ok\n", regno); return -EACCES; } } else { /* check whether register used as dest operand can be written to */ if (regno == BPF_REG_FP) { verbose("frame pointer is read only\n"); return -EACCES; } if (t == DST_OP) mark_reg_unknown_value(regs, regno); } return 0; } static int bpf_size_to_bytes(int bpf_size) { if (bpf_size == BPF_W) return 4; else if (bpf_size == BPF_H) return 2; else if (bpf_size == BPF_B) return 1; else if (bpf_size == BPF_DW) return 8; else return -EINVAL; } static bool is_spillable_regtype(enum bpf_reg_type type) { switch (type) { case PTR_TO_MAP_VALUE: case PTR_TO_MAP_VALUE_OR_NULL: case PTR_TO_MAP_VALUE_ADJ: case PTR_TO_STACK: case PTR_TO_CTX: case PTR_TO_PACKET: case PTR_TO_PACKET_END: case FRAME_PTR: case CONST_PTR_TO_MAP: return true; default: return false; } } /* check_stack_read/write functions track spill/fill of registers, * stack boundary and alignment are checked in check_mem_access() */ static int check_stack_write(struct bpf_verifier_state *state, int off, int size, int value_regno) { int i; /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, * so it's aligned access and [off, off + size) are within stack limits */ if (value_regno >= 0 && is_spillable_regtype(state->regs[value_regno].type)) { /* register containing pointer is being spilled into stack */ if (size != BPF_REG_SIZE) { verbose("invalid size of register spill\n"); return -EACCES; } /* save register state */ state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = state->regs[value_regno]; for (i = 0; i < BPF_REG_SIZE; i++) state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; } else { /* regular write of data into stack */ state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = (struct bpf_reg_state) {}; for (i = 0; i < size; i++) state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; } return 0; } static int check_stack_read(struct bpf_verifier_state *state, int off, int size, int value_regno) { u8 *slot_type; int i; slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; if (slot_type[0] == STACK_SPILL) { if (size != BPF_REG_SIZE) { verbose("invalid size of register spill\n"); return -EACCES; } for (i = 1; i < BPF_REG_SIZE; i++) { if (slot_type[i] != STACK_SPILL) { verbose("corrupted spill memory\n"); return -EACCES; } } if (value_regno >= 0) /* restore register state from stack */ state->regs[value_regno] = state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; return 0; } else { for (i = 0; i < size; i++) { if (slot_type[i] != STACK_MISC) { verbose("invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; } } if (value_regno >= 0) /* have read misc data from the stack */ mark_reg_unknown_value_and_range(state->regs, value_regno); return 0; } } /* check read/write into map element returned by bpf_map_lookup_elem() */ static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off, int size) { struct bpf_map *map = env->cur_state.regs[regno].map_ptr; if (off < 0 || size <= 0 || off + size > map->value_size) { verbose("invalid access to map value, value_size=%d off=%d size=%d\n", map->value_size, off, size); return -EACCES; } return 0; } /* check read/write into an adjusted map element */ static int check_map_access_adj(struct bpf_verifier_env *env, u32 regno, int off, int size) { struct bpf_verifier_state *state = &env->cur_state; struct bpf_reg_state *reg = &state->regs[regno]; int err; /* We adjusted the register to this map value, so we * need to change off and size to min_value and max_value * respectively to make sure our theoretical access will be * safe. */ if (log_level) print_verifier_state(state); env->varlen_map_value_access = true; /* The minimum value is only important with signed * comparisons where we can't assume the floor of a * value is 0. If we are using signed variables for our * index'es we need to make sure that whatever we use * will have a set floor within our range. */ if (reg->min_value < 0) { verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", regno); return -EACCES; } err = check_map_access(env, regno, reg->min_value + off, size); if (err) { verbose("R%d min value is outside of the array range\n", regno); return err; } /* If we haven't set a max value then we need to bail * since we can't be sure we won't do bad things. */ if (reg->max_value == BPF_REGISTER_MAX_RANGE) { verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n", regno); return -EACCES; } return check_map_access(env, regno, reg->max_value + off, size); } #define MAX_PACKET_OFF 0xffff static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, const struct bpf_call_arg_meta *meta, enum bpf_access_type t) { switch (env->prog->type) { case BPF_PROG_TYPE_LWT_IN: case BPF_PROG_TYPE_LWT_OUT: /* dst_input() and dst_output() can't write for now */ if (t == BPF_WRITE) return false; /* fallthrough */ case BPF_PROG_TYPE_SCHED_CLS: case BPF_PROG_TYPE_SCHED_ACT: case BPF_PROG_TYPE_XDP: case BPF_PROG_TYPE_LWT_XMIT: if (meta) return meta->pkt_access; env->seen_direct_write = true; return true; default: return false; } } static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, int size) { struct bpf_reg_state *regs = env->cur_state.regs; struct bpf_reg_state *reg = ®s[regno]; off += reg->off; if (off < 0 || size <= 0 || off + size > reg->range) { verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", off, size, regno, reg->id, reg->off, reg->range); return -EACCES; } return 0; } /* check access to 'struct bpf_context' fields */ static int check_ctx_access(struct bpf_verifier_env *env, int off, int size, enum bpf_access_type t, enum bpf_reg_type *reg_type) { /* for analyzer ctx accesses are already validated and converted */ if (env->analyzer_ops) return 0; if (env->prog->aux->ops->is_valid_access && env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { /* remember the offset of last byte accessed in ctx */ if (env->prog->aux->max_ctx_offset < off + size) env->prog->aux->max_ctx_offset = off + size; return 0; } verbose("invalid bpf_context access off=%d size=%d\n", off, size); return -EACCES; } static bool is_pointer_value(struct bpf_verifier_env *env, int regno) { if (env->allow_ptr_leaks) return false; switch (env->cur_state.regs[regno].type) { case UNKNOWN_VALUE: case CONST_IMM: return false; default: return true; } } static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, int off, int size, bool strict) { int ip_align; int reg_off; /* Byte size accesses are always allowed. */ if (!strict || size == 1) return 0; reg_off = reg->off; if (reg->id) { if (reg->aux_off_align % size) { verbose("Packet access is only %u byte aligned, %d byte access not allowed\n", reg->aux_off_align, size); return -EACCES; } reg_off += reg->aux_off; } /* For platforms that do not have a Kconfig enabling * CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of * NET_IP_ALIGN is universally set to '2'. And on platforms * that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get * to this code only in strict mode where we want to emulate * the NET_IP_ALIGN==2 checking. Therefore use an * unconditional IP align value of '2'. */ ip_align = 2; if ((ip_align + reg_off + off) % size != 0) { verbose("misaligned packet access off %d+%d+%d size %d\n", ip_align, reg_off, off, size); return -EACCES; } return 0; } static int check_val_ptr_alignment(const struct bpf_reg_state *reg, int size, bool strict) { if (strict && size != 1) { verbose("Unknown alignment. Only byte-sized access allowed in value access.\n"); return -EACCES; } return 0; } static int check_ptr_alignment(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, int off, int size) { bool strict = env->strict_alignment; switch (reg->type) { case PTR_TO_PACKET: return check_pkt_ptr_alignment(reg, off, size, strict); case PTR_TO_MAP_VALUE_ADJ: return check_val_ptr_alignment(reg, size, strict); default: if (off % size != 0) { verbose("misaligned access off %d size %d\n", off, size); return -EACCES; } return 0; } } /* check whether memory at (regno + off) is accessible for t = (read | write) * if t==write, value_regno is a register which value is stored into memory * if t==read, value_regno is a register which will receive the value from memory * if t==write && value_regno==-1, some unknown value is stored into memory * if t==read && value_regno==-1, don't care what we read from memory */ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, int bpf_size, enum bpf_access_type t, int value_regno) { struct bpf_verifier_state *state = &env->cur_state; struct bpf_reg_state *reg = &state->regs[regno]; int size, err = 0; if (reg->type == PTR_TO_STACK) off += reg->imm; size = bpf_size_to_bytes(bpf_size); if (size < 0) return size; err = check_ptr_alignment(env, reg, off, size); if (err) return err; if (reg->type == PTR_TO_MAP_VALUE || reg->type == PTR_TO_MAP_VALUE_ADJ) { if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose("R%d leaks addr into map\n", value_regno); return -EACCES; } if (reg->type == PTR_TO_MAP_VALUE_ADJ) err = check_map_access_adj(env, regno, off, size); else err = check_map_access(env, regno, off, size); if (!err && t == BPF_READ && value_regno >= 0) mark_reg_unknown_value_and_range(state->regs, value_regno); } else if (reg->type == PTR_TO_CTX) { enum bpf_reg_type reg_type = UNKNOWN_VALUE; if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose("R%d leaks addr into ctx\n", value_regno); return -EACCES; } err = check_ctx_access(env, off, size, t, ®_type); if (!err && t == BPF_READ && value_regno >= 0) { mark_reg_unknown_value_and_range(state->regs, value_regno); /* note that reg.[id|off|range] == 0 */ state->regs[value_regno].type = reg_type; state->regs[value_regno].aux_off = 0; state->regs[value_regno].aux_off_align = 0; } } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { if (off >= 0 || off < -MAX_BPF_STACK) { verbose("invalid stack off=%d size=%d\n", off, size); return -EACCES; } if (t == BPF_WRITE) { if (!env->allow_ptr_leaks && state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && size != BPF_REG_SIZE) { verbose("attempt to corrupt spilled pointer on stack\n"); return -EACCES; } err = check_stack_write(state, off, size, value_regno); } else { err = check_stack_read(state, off, size, value_regno); } } else if (state->regs[regno].type == PTR_TO_PACKET) { if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) { verbose("cannot write into packet\n"); return -EACCES; } if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose("R%d leaks addr into packet\n", value_regno); return -EACCES; } err = check_packet_access(env, regno, off, size); if (!err && t == BPF_READ && value_regno >= 0) mark_reg_unknown_value_and_range(state->regs, value_regno); } else { verbose("R%d invalid mem access '%s'\n", regno, reg_type_str[reg->type]); return -EACCES; } if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks && state->regs[value_regno].type == UNKNOWN_VALUE) { /* 1 or 2 byte load zero-extends, determine the number of * zero upper bits. Not doing it fo 4 byte load, since * such values cannot be added to ptr_to_packet anyway. */ state->regs[value_regno].imm = 64 - size * 8; } return err; } static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs; int err; if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || insn->imm != 0) { verbose("BPF_XADD uses reserved fields\n"); return -EINVAL; } /* check src1 operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; /* check src2 operand */ err = check_reg_arg(regs, insn->dst_reg, SRC_OP); if (err) return err; /* check whether atomic_add can read the memory */ err = check_mem_access(env, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_READ, -1); if (err) return err; /* check whether atomic_add can write into the same memory */ return check_mem_access(env, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, -1); } /* when register 'regno' is passed into function that will read 'access_size' * bytes from that pointer, make sure that it's within stack boundary * and all elements of stack are initialized */ static int check_stack_boundary(struct bpf_verifier_env *env, int regno, int access_size, bool zero_size_allowed, struct bpf_call_arg_meta *meta) { struct bpf_verifier_state *state = &env->cur_state; struct bpf_reg_state *regs = state->regs; int off, i; if (regs[regno].type != PTR_TO_STACK) { if (zero_size_allowed && access_size == 0 && regs[regno].type == CONST_IMM && regs[regno].imm == 0) return 0; verbose("R%d type=%s expected=%s\n", regno, reg_type_str[regs[regno].type], reg_type_str[PTR_TO_STACK]); return -EACCES; } off = regs[regno].imm; if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || access_size <= 0) { verbose("invalid stack type R%d off=%d access_size=%d\n", regno, off, access_size); return -EACCES; } if (meta && meta->raw_mode) { meta->access_size = access_size; meta->regno = regno; return 0; } for (i = 0; i < access_size; i++) { if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { verbose("invalid indirect read from stack off %d+%d size %d\n", off, i, access_size); return -EACCES; } } return 0; } static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, int access_size, bool zero_size_allowed, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *regs = env->cur_state.regs; switch (regs[regno].type) { case PTR_TO_PACKET: return check_packet_access(env, regno, 0, access_size); case PTR_TO_MAP_VALUE: return check_map_access(env, regno, 0, access_size); case PTR_TO_MAP_VALUE_ADJ: return check_map_access_adj(env, regno, 0, access_size); default: /* const_imm|ptr_to_stack or invalid ptr */ return check_stack_boundary(env, regno, access_size, zero_size_allowed, meta); } } static int check_func_arg(struct bpf_verifier_env *env, u32 regno, enum bpf_arg_type arg_type, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *regs = env->cur_state.regs, *reg = ®s[regno]; enum bpf_reg_type expected_type, type = reg->type; int err = 0; if (arg_type == ARG_DONTCARE) return 0; if (type == NOT_INIT) { verbose("R%d !read_ok\n", regno); return -EACCES; } if (arg_type == ARG_ANYTHING) { if (is_pointer_value(env, regno)) { verbose("R%d leaks addr into helper function\n", regno); return -EACCES; } return 0; } if (type == PTR_TO_PACKET && !may_access_direct_pkt_data(env, meta, BPF_READ)) { verbose("helper access to the packet is not allowed\n"); return -EACCES; } if (arg_type == ARG_PTR_TO_MAP_KEY || arg_type == ARG_PTR_TO_MAP_VALUE) { expected_type = PTR_TO_STACK; if (type != PTR_TO_PACKET && type != expected_type) goto err_type; } else if (arg_type == ARG_CONST_SIZE || arg_type == ARG_CONST_SIZE_OR_ZERO) { expected_type = CONST_IMM; /* One exception. Allow UNKNOWN_VALUE registers when the * boundaries are known and don't cause unsafe memory accesses */ if (type != UNKNOWN_VALUE && type != expected_type) goto err_type; } else if (arg_type == ARG_CONST_MAP_PTR) { expected_type = CONST_PTR_TO_MAP; if (type != expected_type) goto err_type; } else if (arg_type == ARG_PTR_TO_CTX) { expected_type = PTR_TO_CTX; if (type != expected_type) goto err_type; } else if (arg_type == ARG_PTR_TO_MEM || arg_type == ARG_PTR_TO_UNINIT_MEM) { expected_type = PTR_TO_STACK; /* One exception here. In case function allows for NULL to be * passed in as argument, it's a CONST_IMM type. Final test * happens during stack boundary checking. */ if (type == CONST_IMM && reg->imm == 0) /* final test in check_stack_boundary() */; else if (type != PTR_TO_PACKET && type != PTR_TO_MAP_VALUE && type != PTR_TO_MAP_VALUE_ADJ && type != expected_type) goto err_type; meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM; } else { verbose("unsupported arg_type %d\n", arg_type); return -EFAULT; } if (arg_type == ARG_CONST_MAP_PTR) { /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ meta->map_ptr = reg->map_ptr; } else if (arg_type == ARG_PTR_TO_MAP_KEY) { /* bpf_map_xxx(..., map_ptr, ..., key) call: * check that [key, key + map->key_size) are within * stack limits and initialized */ if (!meta->map_ptr) { /* in function declaration map_ptr must come before * map_key, so that it's verified and known before * we have to check map_key here. Otherwise it means * that kernel subsystem misconfigured verifier */ verbose("invalid map_ptr to access map->key\n"); return -EACCES; } if (type == PTR_TO_PACKET) err = check_packet_access(env, regno, 0, meta->map_ptr->key_size); else err = check_stack_boundary(env, regno, meta->map_ptr->key_size, false, NULL); } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { /* bpf_map_xxx(..., map_ptr, ..., value) call: * check [value, value + map->value_size) validity */ if (!meta->map_ptr) { /* kernel subsystem misconfigured verifier */ verbose("invalid map_ptr to access map->value\n"); return -EACCES; } if (type == PTR_TO_PACKET) err = check_packet_access(env, regno, 0, meta->map_ptr->value_size); else err = check_stack_boundary(env, regno, meta->map_ptr->value_size, false, NULL); } else if (arg_type == ARG_CONST_SIZE || arg_type == ARG_CONST_SIZE_OR_ZERO) { bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO); /* bpf_xxx(..., buf, len) call will access 'len' bytes * from stack pointer 'buf'. Check it * note: regno == len, regno - 1 == buf */ if (regno == 0) { /* kernel subsystem misconfigured verifier */ verbose("ARG_CONST_SIZE cannot be first argument\n"); return -EACCES; } /* If the register is UNKNOWN_VALUE, the access check happens * using its boundaries. Otherwise, just use its imm */ if (type == UNKNOWN_VALUE) { /* For unprivileged variable accesses, disable raw * mode so that the program is required to * initialize all the memory that the helper could * just partially fill up. */ meta = NULL; if (reg->min_value < 0) { verbose("R%d min value is negative, either use unsigned or 'var &= const'\n", regno); return -EACCES; } if (reg->min_value == 0) { err = check_helper_mem_access(env, regno - 1, 0, zero_size_allowed, meta); if (err) return err; } if (reg->max_value == BPF_REGISTER_MAX_RANGE) { verbose("R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n", regno); return -EACCES; } err = check_helper_mem_access(env, regno - 1, reg->max_value, zero_size_allowed, meta); if (err) return err; } else { /* register is CONST_IMM */ err = check_helper_mem_access(env, regno - 1, reg->imm, zero_size_allowed, meta); } } return err; err_type: verbose("R%d type=%s expected=%s\n", regno, reg_type_str[type], reg_type_str[expected_type]); return -EACCES; } static int check_map_func_compatibility(struct bpf_map *map, int func_id) { if (!map) return 0; /* We need a two way check, first is from map perspective ... */ switch (map->map_type) { case BPF_MAP_TYPE_PROG_ARRAY: if (func_id != BPF_FUNC_tail_call) goto error; break; case BPF_MAP_TYPE_PERF_EVENT_ARRAY: if (func_id != BPF_FUNC_perf_event_read && func_id != BPF_FUNC_perf_event_output) goto error; break; case BPF_MAP_TYPE_STACK_TRACE: if (func_id != BPF_FUNC_get_stackid) goto error; break; case BPF_MAP_TYPE_CGROUP_ARRAY: if (func_id != BPF_FUNC_skb_under_cgroup && func_id != BPF_FUNC_current_task_under_cgroup) goto error; break; case BPF_MAP_TYPE_ARRAY_OF_MAPS: case BPF_MAP_TYPE_HASH_OF_MAPS: if (func_id != BPF_FUNC_map_lookup_elem) goto error; default: break; } /* ... and second from the function itself. */ switch (func_id) { case BPF_FUNC_tail_call: if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) goto error; break; case BPF_FUNC_perf_event_read: case BPF_FUNC_perf_event_output: if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) goto error; break; case BPF_FUNC_get_stackid: if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) goto error; break; case BPF_FUNC_current_task_under_cgroup: case BPF_FUNC_skb_under_cgroup: if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY) goto error; break; default: break; } return 0; error: verbose("cannot pass map_type %d into func %s#%d\n", map->map_type, func_id_name(func_id), func_id); return -EINVAL; } static int check_raw_mode(const struct bpf_func_proto *fn) { int count = 0; if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM) count++; return count > 1 ? -EINVAL : 0; } static void clear_all_pkt_pointers(struct bpf_verifier_env *env) { struct bpf_verifier_state *state = &env->cur_state; struct bpf_reg_state *regs = state->regs, *reg; int i; for (i = 0; i < MAX_BPF_REG; i++) if (regs[i].type == PTR_TO_PACKET || regs[i].type == PTR_TO_PACKET_END) mark_reg_unknown_value(regs, i); for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { if (state->stack_slot_type[i] != STACK_SPILL) continue; reg = &state->spilled_regs[i / BPF_REG_SIZE]; if (reg->type != PTR_TO_PACKET && reg->type != PTR_TO_PACKET_END) continue; reg->type = UNKNOWN_VALUE; reg->imm = 0; } } static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx) { struct bpf_verifier_state *state = &env->cur_state; const struct bpf_func_proto *fn = NULL; struct bpf_reg_state *regs = state->regs; struct bpf_reg_state *reg; struct bpf_call_arg_meta meta; bool changes_data; int i, err; /* find function prototype */ if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { verbose("invalid func %s#%d\n", func_id_name(func_id), func_id); return -EINVAL; } if (env->prog->aux->ops->get_func_proto) fn = env->prog->aux->ops->get_func_proto(func_id); if (!fn) { verbose("unknown func %s#%d\n", func_id_name(func_id), func_id); return -EINVAL; } /* eBPF programs must be GPL compatible to use GPL-ed functions */ if (!env->prog->gpl_compatible && fn->gpl_only) { verbose("cannot call GPL only function from proprietary program\n"); return -EINVAL; } changes_data = bpf_helper_changes_pkt_data(fn->func); memset(&meta, 0, sizeof(meta)); meta.pkt_access = fn->pkt_access; /* We only support one arg being in raw mode at the moment, which * is sufficient for the helper functions we have right now. */ err = check_raw_mode(fn); if (err) { verbose("kernel subsystem misconfigured func %s#%d\n", func_id_name(func_id), func_id); return err; } /* check args */ err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); if (err) return err; /* Mark slots with STACK_MISC in case of raw mode, stack offset * is inferred from register state. */ for (i = 0; i < meta.access_size; i++) { err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1); if (err) return err; } /* reset caller saved regs */ for (i = 0; i < CALLER_SAVED_REGS; i++) { reg = regs + caller_saved[i]; reg->type = NOT_INIT; reg->imm = 0; } /* update return register */ if (fn->ret_type == RET_INTEGER) { regs[BPF_REG_0].type = UNKNOWN_VALUE; } else if (fn->ret_type == RET_VOID) { regs[BPF_REG_0].type = NOT_INIT; } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { struct bpf_insn_aux_data *insn_aux; regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; regs[BPF_REG_0].max_value = regs[BPF_REG_0].min_value = 0; /* remember map_ptr, so that check_map_access() * can check 'value_size' boundary of memory access * to map element returned from bpf_map_lookup_elem() */ if (meta.map_ptr == NULL) { verbose("kernel subsystem misconfigured verifier\n"); return -EINVAL; } regs[BPF_REG_0].map_ptr = meta.map_ptr; regs[BPF_REG_0].id = ++env->id_gen; insn_aux = &env->insn_aux_data[insn_idx]; if (!insn_aux->map_ptr) insn_aux->map_ptr = meta.map_ptr; else if (insn_aux->map_ptr != meta.map_ptr) insn_aux->map_ptr = BPF_MAP_PTR_POISON; } else { verbose("unknown return type %d of func %s#%d\n", fn->ret_type, func_id_name(func_id), func_id); return -EINVAL; } err = check_map_func_compatibility(meta.map_ptr, func_id); if (err) return err; if (changes_data) clear_all_pkt_pointers(env); return 0; } static int check_packet_ptr_add(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs; struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; struct bpf_reg_state *src_reg = ®s[insn->src_reg]; struct bpf_reg_state tmp_reg; s32 imm; if (BPF_SRC(insn->code) == BPF_K) { /* pkt_ptr += imm */ imm = insn->imm; add_imm: if (imm < 0) { verbose("addition of negative constant to packet pointer is not allowed\n"); return -EACCES; } if (imm >= MAX_PACKET_OFF || imm + dst_reg->off >= MAX_PACKET_OFF) { verbose("constant %d is too large to add to packet pointer\n", imm); return -EACCES; } /* a constant was added to pkt_ptr. * Remember it while keeping the same 'id' */ dst_reg->off += imm; } else { bool had_id; if (src_reg->type == PTR_TO_PACKET) { /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */ tmp_reg = *dst_reg; /* save r7 state */ *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */ src_reg = &tmp_reg; /* pretend it's src_reg state */ /* if the checks below reject it, the copy won't matter, * since we're rejecting the whole program. If all ok, * then imm22 state will be added to r7 * and r7 will be pkt(id=0,off=22,r=62) while * r6 will stay as pkt(id=0,off=0,r=62) */ } if (src_reg->type == CONST_IMM) { /* pkt_ptr += reg where reg is known constant */ imm = src_reg->imm; goto add_imm; } /* disallow pkt_ptr += reg * if reg is not uknown_value with guaranteed zero upper bits * otherwise pkt_ptr may overflow and addition will become * subtraction which is not allowed */ if (src_reg->type != UNKNOWN_VALUE) { verbose("cannot add '%s' to ptr_to_packet\n", reg_type_str[src_reg->type]); return -EACCES; } if (src_reg->imm < 48) { verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n", src_reg->imm); return -EACCES; } had_id = (dst_reg->id != 0); /* dst_reg stays as pkt_ptr type and since some positive * integer value was added to the pointer, increment its 'id' */ dst_reg->id = ++env->id_gen; /* something was added to pkt_ptr, set range to zero */ dst_reg->aux_off += dst_reg->off; dst_reg->off = 0; dst_reg->range = 0; if (had_id) dst_reg->aux_off_align = min(dst_reg->aux_off_align, src_reg->min_align); else dst_reg->aux_off_align = src_reg->min_align; } return 0; } static int evaluate_reg_alu(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs; struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; u8 opcode = BPF_OP(insn->code); s64 imm_log2; /* for type == UNKNOWN_VALUE: * imm > 0 -> number of zero upper bits * imm == 0 -> don't track which is the same as all bits can be non-zero */ if (BPF_SRC(insn->code) == BPF_X) { struct bpf_reg_state *src_reg = ®s[insn->src_reg]; if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 && dst_reg->imm && opcode == BPF_ADD) { /* dreg += sreg * where both have zero upper bits. Adding them * can only result making one more bit non-zero * in the larger value. * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47) * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47) */ dst_reg->imm = min(dst_reg->imm, src_reg->imm); dst_reg->imm--; return 0; } if (src_reg->type == CONST_IMM && src_reg->imm > 0 && dst_reg->imm && opcode == BPF_ADD) { /* dreg += sreg * where dreg has zero upper bits and sreg is const. * Adding them can only result making one more bit * non-zero in the larger value. */ imm_log2 = __ilog2_u64((long long)src_reg->imm); dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); dst_reg->imm--; return 0; } /* all other cases non supported yet, just mark dst_reg */ dst_reg->imm = 0; return 0; } /* sign extend 32-bit imm into 64-bit to make sure that * negative values occupy bit 63. Note ilog2() would have * been incorrect, since sizeof(insn->imm) == 4 */ imm_log2 = __ilog2_u64((long long)insn->imm); if (dst_reg->imm && opcode == BPF_LSH) { /* reg <<= imm * if reg was a result of 2 byte load, then its imm == 48 * which means that upper 48 bits are zero and shifting this reg * left by 4 would mean that upper 44 bits are still zero */ dst_reg->imm -= insn->imm; } else if (dst_reg->imm && opcode == BPF_MUL) { /* reg *= imm * if multiplying by 14 subtract 4 * This is conservative calculation of upper zero bits. * It's not trying to special case insn->imm == 1 or 0 cases */ dst_reg->imm -= imm_log2 + 1; } else if (opcode == BPF_AND) { /* reg &= imm */ dst_reg->imm = 63 - imm_log2; } else if (dst_reg->imm && opcode == BPF_ADD) { /* reg += imm */ dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); dst_reg->imm--; } else if (opcode == BPF_RSH) { /* reg >>= imm * which means that after right shift, upper bits will be zero * note that verifier already checked that * 0 <= imm < 64 for shift insn */ dst_reg->imm += insn->imm; if (unlikely(dst_reg->imm > 64)) /* some dumb code did: * r2 = *(u32 *)mem; * r2 >>= 32; * and all bits are zero now */ dst_reg->imm = 64; } else { /* all other alu ops, means that we don't know what will * happen to the value, mark it with unknown number of zero bits */ dst_reg->imm = 0; } if (dst_reg->imm < 0) { /* all 64 bits of the register can contain non-zero bits * and such value cannot be added to ptr_to_packet, since it * may overflow, mark it as unknown to avoid further eval */ dst_reg->imm = 0; } return 0; } static int evaluate_reg_imm_alu(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs; struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; struct bpf_reg_state *src_reg = ®s[insn->src_reg]; u8 opcode = BPF_OP(insn->code); u64 dst_imm = dst_reg->imm; /* dst_reg->type == CONST_IMM here. Simulate execution of insns * containing ALU ops. Don't care about overflow or negative * values, just add/sub/... them; registers are in u64. */ if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) { dst_imm += insn->imm; } else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm += src_reg->imm; } else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_K) { dst_imm -= insn->imm; } else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm -= src_reg->imm; } else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_K) { dst_imm *= insn->imm; } else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm *= src_reg->imm; } else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_K) { dst_imm |= insn->imm; } else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm |= src_reg->imm; } else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_K) { dst_imm &= insn->imm; } else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm &= src_reg->imm; } else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_K) { dst_imm >>= insn->imm; } else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm >>= src_reg->imm; } else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_K) { dst_imm <<= insn->imm; } else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) { dst_imm <<= src_reg->imm; } else { mark_reg_unknown_value(regs, insn->dst_reg); goto out; } dst_reg->imm = dst_imm; out: return 0; } static void check_reg_overflow(struct bpf_reg_state *reg) { if (reg->max_value > BPF_REGISTER_MAX_RANGE) reg->max_value = BPF_REGISTER_MAX_RANGE; if (reg->min_value < BPF_REGISTER_MIN_RANGE || reg->min_value > BPF_REGISTER_MAX_RANGE) reg->min_value = BPF_REGISTER_MIN_RANGE; } static u32 calc_align(u32 imm) { if (!imm) return 1U << 31; return imm - ((imm - 1) & imm); } static void adjust_reg_min_max_vals(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; s64 min_val = BPF_REGISTER_MIN_RANGE; u64 max_val = BPF_REGISTER_MAX_RANGE; u8 opcode = BPF_OP(insn->code); u32 dst_align, src_align; dst_reg = ®s[insn->dst_reg]; src_align = 0; if (BPF_SRC(insn->code) == BPF_X) { check_reg_overflow(®s[insn->src_reg]); min_val = regs[insn->src_reg].min_value; max_val = regs[insn->src_reg].max_value; /* If the source register is a random pointer then the * min_value/max_value values represent the range of the known * accesses into that value, not the actual min/max value of the * register itself. In this case we have to reset the reg range * values so we know it is not safe to look at. */ if (regs[insn->src_reg].type != CONST_IMM && regs[insn->src_reg].type != UNKNOWN_VALUE) { min_val = BPF_REGISTER_MIN_RANGE; max_val = BPF_REGISTER_MAX_RANGE; src_align = 0; } else { src_align = regs[insn->src_reg].min_align; } } else if (insn->imm < BPF_REGISTER_MAX_RANGE && (s64)insn->imm > BPF_REGISTER_MIN_RANGE) { min_val = max_val = insn->imm; src_align = calc_align(insn->imm); } dst_align = dst_reg->min_align; /* We don't know anything about what was done to this register, mark it * as unknown. */ if (min_val == BPF_REGISTER_MIN_RANGE && max_val == BPF_REGISTER_MAX_RANGE) { reset_reg_range_values(regs, insn->dst_reg); return; } /* If one of our values was at the end of our ranges then we can't just * do our normal operations to the register, we need to set the values * to the min/max since they are undefined. */ if (min_val == BPF_REGISTER_MIN_RANGE) dst_reg->min_value = BPF_REGISTER_MIN_RANGE; if (max_val == BPF_REGISTER_MAX_RANGE) dst_reg->max_value = BPF_REGISTER_MAX_RANGE; switch (opcode) { case BPF_ADD: if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) dst_reg->min_value += min_val; if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) dst_reg->max_value += max_val; dst_reg->min_align = min(src_align, dst_align); break; case BPF_SUB: if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) dst_reg->min_value -= min_val; if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) dst_reg->max_value -= max_val; dst_reg->min_align = min(src_align, dst_align); break; case BPF_MUL: if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) dst_reg->min_value *= min_val; if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) dst_reg->max_value *= max_val; dst_reg->min_align = max(src_align, dst_align); break; case BPF_AND: /* Disallow AND'ing of negative numbers, ain't nobody got time * for that. Otherwise the minimum is 0 and the max is the max * value we could AND against. */ if (min_val < 0) dst_reg->min_value = BPF_REGISTER_MIN_RANGE; else dst_reg->min_value = 0; dst_reg->max_value = max_val; dst_reg->min_align = max(src_align, dst_align); break; case BPF_LSH: /* Gotta have special overflow logic here, if we're shifting * more than MAX_RANGE then just assume we have an invalid * range. */ if (min_val > ilog2(BPF_REGISTER_MAX_RANGE)) { dst_reg->min_value = BPF_REGISTER_MIN_RANGE; dst_reg->min_align = 1; } else { if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) dst_reg->min_value <<= min_val; if (!dst_reg->min_align) dst_reg->min_align = 1; dst_reg->min_align <<= min_val; } if (max_val > ilog2(BPF_REGISTER_MAX_RANGE)) dst_reg->max_value = BPF_REGISTER_MAX_RANGE; else if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) dst_reg->max_value <<= max_val; break; case BPF_RSH: /* RSH by a negative number is undefined, and the BPF_RSH is an * unsigned shift, so make the appropriate casts. */ if (min_val < 0 || dst_reg->min_value < 0) { dst_reg->min_value = BPF_REGISTER_MIN_RANGE; } else { dst_reg->min_value = (u64)(dst_reg->min_value) >> min_val; } if (min_val < 0) { dst_reg->min_align = 1; } else { dst_reg->min_align >>= (u64) min_val; if (!dst_reg->min_align) dst_reg->min_align = 1; } if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) dst_reg->max_value >>= max_val; break; default: reset_reg_range_values(regs, insn->dst_reg); break; } check_reg_overflow(dst_reg); } /* check validity of 32-bit and 64-bit arithmetic operations */ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; u8 opcode = BPF_OP(insn->code); int err; if (opcode == BPF_END || opcode == BPF_NEG) { if (opcode == BPF_NEG) { if (BPF_SRC(insn->code) != 0 || insn->src_reg != BPF_REG_0 || insn->off != 0 || insn->imm != 0) { verbose("BPF_NEG uses reserved fields\n"); return -EINVAL; } } else { if (insn->src_reg != BPF_REG_0 || insn->off != 0 || (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { verbose("BPF_END uses reserved fields\n"); return -EINVAL; } } /* check src operand */ err = check_reg_arg(regs, insn->dst_reg, SRC_OP); if (err) return err; if (is_pointer_value(env, insn->dst_reg)) { verbose("R%d pointer arithmetic prohibited\n", insn->dst_reg); return -EACCES; } /* check dest operand */ err = check_reg_arg(regs, insn->dst_reg, DST_OP); if (err) return err; } else if (opcode == BPF_MOV) { if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0 || insn->off != 0) { verbose("BPF_MOV uses reserved fields\n"); return -EINVAL; } /* check src operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; } else { if (insn->src_reg != BPF_REG_0 || insn->off != 0) { verbose("BPF_MOV uses reserved fields\n"); return -EINVAL; } } /* check dest operand */ err = check_reg_arg(regs, insn->dst_reg, DST_OP); if (err) return err; /* we are setting our register to something new, we need to * reset its range values. */ reset_reg_range_values(regs, insn->dst_reg); if (BPF_SRC(insn->code) == BPF_X) { if (BPF_CLASS(insn->code) == BPF_ALU64) { /* case: R1 = R2 * copy register state to dest reg */ regs[insn->dst_reg] = regs[insn->src_reg]; } else { if (is_pointer_value(env, insn->src_reg)) { verbose("R%d partial copy of pointer\n", insn->src_reg); return -EACCES; } mark_reg_unknown_value(regs, insn->dst_reg); } } else { /* case: R = imm * remember the value we stored into this reg */ regs[insn->dst_reg].type = CONST_IMM; regs[insn->dst_reg].imm = insn->imm; regs[insn->dst_reg].max_value = insn->imm; regs[insn->dst_reg].min_value = insn->imm; regs[insn->dst_reg].min_align = calc_align(insn->imm); } } else if (opcode > BPF_END) { verbose("invalid BPF_ALU opcode %x\n", opcode); return -EINVAL; } else { /* all other ALU ops: and, sub, xor, add, ... */ if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0 || insn->off != 0) { verbose("BPF_ALU uses reserved fields\n"); return -EINVAL; } /* check src1 operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; } else { if (insn->src_reg != BPF_REG_0 || insn->off != 0) { verbose("BPF_ALU uses reserved fields\n"); return -EINVAL; } } /* check src2 operand */ err = check_reg_arg(regs, insn->dst_reg, SRC_OP); if (err) return err; if ((opcode == BPF_MOD || opcode == BPF_DIV) && BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { verbose("div by zero\n"); return -EINVAL; } if ((opcode == BPF_LSH || opcode == BPF_RSH || opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; if (insn->imm < 0 || insn->imm >= size) { verbose("invalid shift %d\n", insn->imm); return -EINVAL; } } /* check dest operand */ err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); if (err) return err; dst_reg = ®s[insn->dst_reg]; /* first we want to adjust our ranges. */ adjust_reg_min_max_vals(env, insn); /* pattern match 'bpf_add Rx, imm' instruction */ if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) { dst_reg->type = PTR_TO_STACK; dst_reg->imm = insn->imm; return 0; } else if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && dst_reg->type == PTR_TO_STACK && ((BPF_SRC(insn->code) == BPF_X && regs[insn->src_reg].type == CONST_IMM) || BPF_SRC(insn->code) == BPF_K)) { if (BPF_SRC(insn->code) == BPF_X) dst_reg->imm += regs[insn->src_reg].imm; else dst_reg->imm += insn->imm; return 0; } else if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && (dst_reg->type == PTR_TO_PACKET || (BPF_SRC(insn->code) == BPF_X && regs[insn->src_reg].type == PTR_TO_PACKET))) { /* ptr_to_packet += K|X */ return check_packet_ptr_add(env, insn); } else if (BPF_CLASS(insn->code) == BPF_ALU64 && dst_reg->type == UNKNOWN_VALUE && env->allow_ptr_leaks) { /* unknown += K|X */ return evaluate_reg_alu(env, insn); } else if (BPF_CLASS(insn->code) == BPF_ALU64 && dst_reg->type == CONST_IMM && env->allow_ptr_leaks) { /* reg_imm += K|X */ return evaluate_reg_imm_alu(env, insn); } else if (is_pointer_value(env, insn->dst_reg)) { verbose("R%d pointer arithmetic prohibited\n", insn->dst_reg); return -EACCES; } else if (BPF_SRC(insn->code) == BPF_X && is_pointer_value(env, insn->src_reg)) { verbose("R%d pointer arithmetic prohibited\n", insn->src_reg); return -EACCES; } /* If we did pointer math on a map value then just set it to our * PTR_TO_MAP_VALUE_ADJ type so we can deal with any stores or * loads to this register appropriately, otherwise just mark the * register as unknown. */ if (env->allow_ptr_leaks && BPF_CLASS(insn->code) == BPF_ALU64 && opcode == BPF_ADD && (dst_reg->type == PTR_TO_MAP_VALUE || dst_reg->type == PTR_TO_MAP_VALUE_ADJ)) dst_reg->type = PTR_TO_MAP_VALUE_ADJ; else mark_reg_unknown_value(regs, insn->dst_reg); } return 0; } static void find_good_pkt_pointers(struct bpf_verifier_state *state, struct bpf_reg_state *dst_reg) { struct bpf_reg_state *regs = state->regs, *reg; int i; /* LLVM can generate two kind of checks: * * Type 1: * * r2 = r3; * r2 += 8; * if (r2 > pkt_end) goto * * * Where: * r2 == dst_reg, pkt_end == src_reg * r2=pkt(id=n,off=8,r=0) * r3=pkt(id=n,off=0,r=0) * * Type 2: * * r2 = r3; * r2 += 8; * if (pkt_end >= r2) goto * * * Where: * pkt_end == dst_reg, r2 == src_reg * r2=pkt(id=n,off=8,r=0) * r3=pkt(id=n,off=0,r=0) * * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) * so that range of bytes [r3, r3 + 8) is safe to access. */ for (i = 0; i < MAX_BPF_REG; i++) if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) /* keep the maximum range already checked */ regs[i].range = max(regs[i].range, dst_reg->off); for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { if (state->stack_slot_type[i] != STACK_SPILL) continue; reg = &state->spilled_regs[i / BPF_REG_SIZE]; if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) reg->range = max(reg->range, dst_reg->off); } } /* Adjusts the register min/max values in the case that the dst_reg is the * variable register that we are working on, and src_reg is a constant or we're * simply doing a BPF_K check. */ static void reg_set_min_max(struct bpf_reg_state *true_reg, struct bpf_reg_state *false_reg, u64 val, u8 opcode) { switch (opcode) { case BPF_JEQ: /* If this is false then we know nothing Jon Snow, but if it is * true then we know for sure. */ true_reg->max_value = true_reg->min_value = val; break; case BPF_JNE: /* If this is true we know nothing Jon Snow, but if it is false * we know the value for sure; */ false_reg->max_value = false_reg->min_value = val; break; case BPF_JGT: /* Unsigned comparison, the minimum value is 0. */ false_reg->min_value = 0; /* fallthrough */ case BPF_JSGT: /* If this is false then we know the maximum val is val, * otherwise we know the min val is val+1. */ false_reg->max_value = val; true_reg->min_value = val + 1; break; case BPF_JGE: /* Unsigned comparison, the minimum value is 0. */ false_reg->min_value = 0; /* fallthrough */ case BPF_JSGE: /* If this is false then we know the maximum value is val - 1, * otherwise we know the mimimum value is val. */ false_reg->max_value = val - 1; true_reg->min_value = val; break; default: break; } check_reg_overflow(false_reg); check_reg_overflow(true_reg); } /* Same as above, but for the case that dst_reg is a CONST_IMM reg and src_reg * is the variable reg. */ static void reg_set_min_max_inv(struct bpf_reg_state *true_reg, struct bpf_reg_state *false_reg, u64 val, u8 opcode) { switch (opcode) { case BPF_JEQ: /* If this is false then we know nothing Jon Snow, but if it is * true then we know for sure. */ true_reg->max_value = true_reg->min_value = val; break; case BPF_JNE: /* If this is true we know nothing Jon Snow, but if it is false * we know the value for sure; */ false_reg->max_value = false_reg->min_value = val; break; case BPF_JGT: /* Unsigned comparison, the minimum value is 0. */ true_reg->min_value = 0; /* fallthrough */ case BPF_JSGT: /* * If this is false, then the val is <= the register, if it is * true the register <= to the val. */ false_reg->min_value = val; true_reg->max_value = val - 1; break; case BPF_JGE: /* Unsigned comparison, the minimum value is 0. */ true_reg->min_value = 0; /* fallthrough */ case BPF_JSGE: /* If this is false then constant < register, if it is true then * the register < constant. */ false_reg->min_value = val + 1; true_reg->max_value = val; break; default: break; } check_reg_overflow(false_reg); check_reg_overflow(true_reg); } static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id, enum bpf_reg_type type) { struct bpf_reg_state *reg = ®s[regno]; if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) { if (type == UNKNOWN_VALUE) { __mark_reg_unknown_value(regs, regno); } else if (reg->map_ptr->inner_map_meta) { reg->type = CONST_PTR_TO_MAP; reg->map_ptr = reg->map_ptr->inner_map_meta; } else { reg->type = type; } /* We don't need id from this point onwards anymore, thus we * should better reset it, so that state pruning has chances * to take effect. */ reg->id = 0; } } /* The logic is similar to find_good_pkt_pointers(), both could eventually * be folded together at some point. */ static void mark_map_regs(struct bpf_verifier_state *state, u32 regno, enum bpf_reg_type type) { struct bpf_reg_state *regs = state->regs; u32 id = regs[regno].id; int i; for (i = 0; i < MAX_BPF_REG; i++) mark_map_reg(regs, i, id, type); for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { if (state->stack_slot_type[i] != STACK_SPILL) continue; mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE, id, type); } } static int check_cond_jmp_op(struct bpf_verifier_env *env, struct bpf_insn *insn, int *insn_idx) { struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state; struct bpf_reg_state *regs = this_branch->regs, *dst_reg; u8 opcode = BPF_OP(insn->code); int err; if (opcode > BPF_EXIT) { verbose("invalid BPF_JMP opcode %x\n", opcode); return -EINVAL; } if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0) { verbose("BPF_JMP uses reserved fields\n"); return -EINVAL; } /* check src1 operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; if (is_pointer_value(env, insn->src_reg)) { verbose("R%d pointer comparison prohibited\n", insn->src_reg); return -EACCES; } } else { if (insn->src_reg != BPF_REG_0) { verbose("BPF_JMP uses reserved fields\n"); return -EINVAL; } } /* check src2 operand */ err = check_reg_arg(regs, insn->dst_reg, SRC_OP); if (err) return err; dst_reg = ®s[insn->dst_reg]; /* detect if R == 0 where R was initialized to zero earlier */ if (BPF_SRC(insn->code) == BPF_K && (opcode == BPF_JEQ || opcode == BPF_JNE) && dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) { if (opcode == BPF_JEQ) { /* if (imm == imm) goto pc+off; * only follow the goto, ignore fall-through */ *insn_idx += insn->off; return 0; } else { /* if (imm != imm) goto pc+off; * only follow fall-through branch, since * that's where the program will go */ return 0; } } other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); if (!other_branch) return -EFAULT; /* detect if we are comparing against a constant value so we can adjust * our min/max values for our dst register. */ if (BPF_SRC(insn->code) == BPF_X) { if (regs[insn->src_reg].type == CONST_IMM) reg_set_min_max(&other_branch->regs[insn->dst_reg], dst_reg, regs[insn->src_reg].imm, opcode); else if (dst_reg->type == CONST_IMM) reg_set_min_max_inv(&other_branch->regs[insn->src_reg], ®s[insn->src_reg], dst_reg->imm, opcode); } else { reg_set_min_max(&other_branch->regs[insn->dst_reg], dst_reg, insn->imm, opcode); } /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */ if (BPF_SRC(insn->code) == BPF_K && insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { /* Mark all identical map registers in each branch as either * safe or unknown depending R == 0 or R != 0 conditional. */ mark_map_regs(this_branch, insn->dst_reg, opcode == BPF_JEQ ? PTR_TO_MAP_VALUE : UNKNOWN_VALUE); mark_map_regs(other_branch, insn->dst_reg, opcode == BPF_JEQ ? UNKNOWN_VALUE : PTR_TO_MAP_VALUE); } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && dst_reg->type == PTR_TO_PACKET && regs[insn->src_reg].type == PTR_TO_PACKET_END) { find_good_pkt_pointers(this_branch, dst_reg); } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && dst_reg->type == PTR_TO_PACKET_END && regs[insn->src_reg].type == PTR_TO_PACKET) { find_good_pkt_pointers(other_branch, ®s[insn->src_reg]); } else if (is_pointer_value(env, insn->dst_reg)) { verbose("R%d pointer comparison prohibited\n", insn->dst_reg); return -EACCES; } if (log_level) print_verifier_state(this_branch); return 0; } /* return the map pointer stored inside BPF_LD_IMM64 instruction */ static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) { u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; return (struct bpf_map *) (unsigned long) imm64; } /* verify BPF_LD_IMM64 instruction */ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs; int err; if (BPF_SIZE(insn->code) != BPF_DW) { verbose("invalid BPF_LD_IMM insn\n"); return -EINVAL; } if (insn->off != 0) { verbose("BPF_LD_IMM64 uses reserved fields\n"); return -EINVAL; } err = check_reg_arg(regs, insn->dst_reg, DST_OP); if (err) return err; if (insn->src_reg == 0) { u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; regs[insn->dst_reg].type = CONST_IMM; regs[insn->dst_reg].imm = imm; return 0; } /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); regs[insn->dst_reg].type = CONST_PTR_TO_MAP; regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); return 0; } static bool may_access_skb(enum bpf_prog_type type) { switch (type) { case BPF_PROG_TYPE_SOCKET_FILTER: case BPF_PROG_TYPE_SCHED_CLS: case BPF_PROG_TYPE_SCHED_ACT: return true; default: return false; } } /* verify safety of LD_ABS|LD_IND instructions: * - they can only appear in the programs where ctx == skb * - since they are wrappers of function calls, they scratch R1-R5 registers, * preserve R6-R9, and store return value into R0 * * Implicit input: * ctx == skb == R6 == CTX * * Explicit input: * SRC == any register * IMM == 32-bit immediate * * Output: * R0 - 8/16/32-bit skb data converted to cpu endianness */ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = env->cur_state.regs; u8 mode = BPF_MODE(insn->code); struct bpf_reg_state *reg; int i, err; if (!may_access_skb(env->prog->type)) { verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); return -EINVAL; } if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || BPF_SIZE(insn->code) == BPF_DW || (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { verbose("BPF_LD_[ABS|IND] uses reserved fields\n"); return -EINVAL; } /* check whether implicit source operand (register R6) is readable */ err = check_reg_arg(regs, BPF_REG_6, SRC_OP); if (err) return err; if (regs[BPF_REG_6].type != PTR_TO_CTX) { verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); return -EINVAL; } if (mode == BPF_IND) { /* check explicit source operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; } /* reset caller saved regs to unreadable */ for (i = 0; i < CALLER_SAVED_REGS; i++) { reg = regs + caller_saved[i]; reg->type = NOT_INIT; reg->imm = 0; } /* mark destination R0 register as readable, since it contains * the value fetched from the packet */ regs[BPF_REG_0].type = UNKNOWN_VALUE; return 0; } /* non-recursive DFS pseudo code * 1 procedure DFS-iterative(G,v): * 2 label v as discovered * 3 let S be a stack * 4 S.push(v) * 5 while S is not empty * 6 t <- S.pop() * 7 if t is what we're looking for: * 8 return t * 9 for all edges e in G.adjacentEdges(t) do * 10 if edge e is already labelled * 11 continue with the next edge * 12 w <- G.adjacentVertex(t,e) * 13 if vertex w is not discovered and not explored * 14 label e as tree-edge * 15 label w as discovered * 16 S.push(w) * 17 continue at 5 * 18 else if vertex w is discovered * 19 label e as back-edge * 20 else * 21 // vertex w is explored * 22 label e as forward- or cross-edge * 23 label t as explored * 24 S.pop() * * convention: * 0x10 - discovered * 0x11 - discovered and fall-through edge labelled * 0x12 - discovered and fall-through and branch edges labelled * 0x20 - explored */ enum { DISCOVERED = 0x10, EXPLORED = 0x20, FALLTHROUGH = 1, BRANCH = 2, }; #define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L) static int *insn_stack; /* stack of insns to process */ static int cur_stack; /* current stack index */ static int *insn_state; /* t, w, e - match pseudo-code above: * t - index of current instruction * w - next instruction * e - edge */ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) { if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) return 0; if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) return 0; if (w < 0 || w >= env->prog->len) { verbose("jump out of range from insn %d to %d\n", t, w); return -EINVAL; } if (e == BRANCH) /* mark branch target for state pruning */ env->explored_states[w] = STATE_LIST_MARK; if (insn_state[w] == 0) { /* tree-edge */ insn_state[t] = DISCOVERED | e; insn_state[w] = DISCOVERED; if (cur_stack >= env->prog->len) return -E2BIG; insn_stack[cur_stack++] = w; return 1; } else if ((insn_state[w] & 0xF0) == DISCOVERED) { verbose("back-edge from insn %d to %d\n", t, w); return -EINVAL; } else if (insn_state[w] == EXPLORED) { /* forward- or cross-edge */ insn_state[t] = DISCOVERED | e; } else { verbose("insn state internal bug\n"); return -EFAULT; } return 0; } /* non-recursive depth-first-search to detect loops in BPF program * loop == back-edge in directed graph */ static int check_cfg(struct bpf_verifier_env *env) { struct bpf_insn *insns = env->prog->insnsi; int insn_cnt = env->prog->len; int ret = 0; int i, t; insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); if (!insn_state) return -ENOMEM; insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); if (!insn_stack) { kfree(insn_state); return -ENOMEM; } insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ insn_stack[0] = 0; /* 0 is the first instruction */ cur_stack = 1; peek_stack: if (cur_stack == 0) goto check_state; t = insn_stack[cur_stack - 1]; if (BPF_CLASS(insns[t].code) == BPF_JMP) { u8 opcode = BPF_OP(insns[t].code); if (opcode == BPF_EXIT) { goto mark_explored; } else if (opcode == BPF_CALL) { ret = push_insn(t, t + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; if (t + 1 < insn_cnt) env->explored_states[t + 1] = STATE_LIST_MARK; } else if (opcode == BPF_JA) { if (BPF_SRC(insns[t].code) != BPF_K) { ret = -EINVAL; goto err_free; } /* unconditional jump with single edge */ ret = push_insn(t, t + insns[t].off + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; /* tell verifier to check for equivalent states * after every call and jump */ if (t + 1 < insn_cnt) env->explored_states[t + 1] = STATE_LIST_MARK; } else { /* conditional jump with two edges */ env->explored_states[t] = STATE_LIST_MARK; ret = push_insn(t, t + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; } } else { /* all other non-branch instructions with single * fall-through edge */ ret = push_insn(t, t + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; } mark_explored: insn_state[t] = EXPLORED; if (cur_stack-- <= 0) { verbose("pop stack internal bug\n"); ret = -EFAULT; goto err_free; } goto peek_stack; check_state: for (i = 0; i < insn_cnt; i++) { if (insn_state[i] != EXPLORED) { verbose("unreachable insn %d\n", i); ret = -EINVAL; goto err_free; } } ret = 0; /* cfg looks good */ err_free: kfree(insn_state); kfree(insn_stack); return ret; } /* the following conditions reduce the number of explored insns * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet */ static bool compare_ptrs_to_packet(struct bpf_verifier_env *env, struct bpf_reg_state *old, struct bpf_reg_state *cur) { if (old->id != cur->id) return false; /* old ptr_to_packet is more conservative, since it allows smaller * range. Ex: * old(off=0,r=10) is equal to cur(off=0,r=20), because * old(off=0,r=10) means that with range=10 the verifier proceeded * further and found no issues with the program. Now we're in the same * spot with cur(off=0,r=20), so we're safe too, since anything further * will only be looking at most 10 bytes after this pointer. */ if (old->off == cur->off && old->range < cur->range) return true; /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0) * since both cannot be used for packet access and safe(old) * pointer has smaller off that could be used for further * 'if (ptr > data_end)' check * Ex: * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean * that we cannot access the packet. * The safe range is: * [ptr, ptr + range - off) * so whenever off >=range, it means no safe bytes from this pointer. * When comparing old->off <= cur->off, it means that older code * went with smaller offset and that offset was later * used to figure out the safe range after 'if (ptr > data_end)' check * Say, 'old' state was explored like: * ... R3(off=0, r=0) * R4 = R3 + 20 * ... now R4(off=20,r=0) <-- here * if (R4 > data_end) * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access. * ... the code further went all the way to bpf_exit. * Now the 'cur' state at the mark 'here' has R4(off=30,r=0). * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier * goes further, such cur_R4 will give larger safe packet range after * 'if (R4 > data_end)' and all further insn were already good with r=20, * so they will be good with r=30 and we can prune the search. */ if (!env->strict_alignment && old->off <= cur->off && old->off >= old->range && cur->off >= cur->range) return true; return false; } /* compare two verifier states * * all states stored in state_list are known to be valid, since * verifier reached 'bpf_exit' instruction through them * * this function is called when verifier exploring different branches of * execution popped from the state stack. If it sees an old state that has * more strict register state and more strict stack state then this execution * branch doesn't need to be explored further, since verifier already * concluded that more strict state leads to valid finish. * * Therefore two states are equivalent if register state is more conservative * and explored stack state is more conservative than the current one. * Example: * explored current * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) * * In other words if current stack state (one being explored) has more * valid slots than old one that already passed validation, it means * the verifier can stop exploring and conclude that current state is valid too * * Similarly with registers. If explored state has register type as invalid * whereas register type in current state is meaningful, it means that * the current state will reach 'bpf_exit' instruction safely */ static bool states_equal(struct bpf_verifier_env *env, struct bpf_verifier_state *old, struct bpf_verifier_state *cur) { bool varlen_map_access = env->varlen_map_value_access; struct bpf_reg_state *rold, *rcur; int i; for (i = 0; i < MAX_BPF_REG; i++) { rold = &old->regs[i]; rcur = &cur->regs[i]; if (memcmp(rold, rcur, sizeof(*rold)) == 0) continue; /* If the ranges were not the same, but everything else was and * we didn't do a variable access into a map then we are a-ok. */ if (!varlen_map_access && memcmp(rold, rcur, offsetofend(struct bpf_reg_state, id)) == 0) continue; /* If we didn't map access then again we don't care about the * mismatched range values and it's ok if our old type was * UNKNOWN and we didn't go to a NOT_INIT'ed reg. */ if (rold->type == NOT_INIT || (!varlen_map_access && rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT)) continue; /* Don't care about the reg->id in this case. */ if (rold->type == PTR_TO_MAP_VALUE_OR_NULL && rcur->type == PTR_TO_MAP_VALUE_OR_NULL && rold->map_ptr == rcur->map_ptr) continue; if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && compare_ptrs_to_packet(env, rold, rcur)) continue; return false; } for (i = 0; i < MAX_BPF_STACK; i++) { if (old->stack_slot_type[i] == STACK_INVALID) continue; if (old->stack_slot_type[i] != cur->stack_slot_type[i]) /* Ex: old explored (safe) state has STACK_SPILL in * this stack slot, but current has has STACK_MISC -> * this verifier states are not equivalent, * return false to continue verification of this path */ return false; if (i % BPF_REG_SIZE) continue; if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], &cur->spilled_regs[i / BPF_REG_SIZE], sizeof(old->spilled_regs[0]))) /* when explored and current stack slot types are * the same, check that stored pointers types * are the same as well. * Ex: explored safe path could have stored * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -8} * but current path has stored: * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -16} * such verifier states are not equivalent. * return false to continue verification of this path */ return false; else continue; } return true; } static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) { struct bpf_verifier_state_list *new_sl; struct bpf_verifier_state_list *sl; sl = env->explored_states[insn_idx]; if (!sl) /* this 'insn_idx' instruction wasn't marked, so we will not * be doing state search here */ return 0; while (sl != STATE_LIST_MARK) { if (states_equal(env, &sl->state, &env->cur_state)) /* reached equivalent register/stack state, * prune the search */ return 1; sl = sl->next; } /* there were no equivalent states, remember current one. * technically the current state is not proven to be safe yet, * but it will either reach bpf_exit (which means it's safe) or * it will be rejected. Since there are no loops, we won't be * seeing this 'insn_idx' instruction again on the way to bpf_exit */ new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER); if (!new_sl) return -ENOMEM; /* add new state to the head of linked list */ memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); new_sl->next = env->explored_states[insn_idx]; env->explored_states[insn_idx] = new_sl; return 0; } static int ext_analyzer_insn_hook(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx) { if (!env->analyzer_ops || !env->analyzer_ops->insn_hook) return 0; return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx); } static int do_check(struct bpf_verifier_env *env) { struct bpf_verifier_state *state = &env->cur_state; struct bpf_insn *insns = env->prog->insnsi; struct bpf_reg_state *regs = state->regs; int insn_cnt = env->prog->len; int insn_idx, prev_insn_idx = 0; int insn_processed = 0; bool do_print_state = false; init_reg_state(regs); insn_idx = 0; env->varlen_map_value_access = false; for (;;) { struct bpf_insn *insn; u8 class; int err; if (insn_idx >= insn_cnt) { verbose("invalid insn idx %d insn_cnt %d\n", insn_idx, insn_cnt); return -EFAULT; } insn = &insns[insn_idx]; class = BPF_CLASS(insn->code); if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { verbose("BPF program is too large. Processed %d insn\n", insn_processed); return -E2BIG; } err = is_state_visited(env, insn_idx); if (err < 0) return err; if (err == 1) { /* found equivalent state, can prune the search */ if (log_level) { if (do_print_state) verbose("\nfrom %d to %d: safe\n", prev_insn_idx, insn_idx); else verbose("%d: safe\n", insn_idx); } goto process_bpf_exit; } if (need_resched()) cond_resched(); if (log_level > 1 || (log_level && do_print_state)) { if (log_level > 1) verbose("%d:", insn_idx); else verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); print_verifier_state(&env->cur_state); do_print_state = false; } if (log_level) { verbose("%d: ", insn_idx); print_bpf_insn(env, insn); } err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx); if (err) return err; if (class == BPF_ALU || class == BPF_ALU64) { err = check_alu_op(env, insn); if (err) return err; } else if (class == BPF_LDX) { enum bpf_reg_type *prev_src_type, src_reg_type; /* check for reserved fields is already done */ /* check src operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); if (err) return err; src_reg_type = regs[insn->src_reg].type; /* check that memory (src_reg + off) is readable, * the state of dst_reg will be updated by this func */ err = check_mem_access(env, insn->src_reg, insn->off, BPF_SIZE(insn->code), BPF_READ, insn->dst_reg); if (err) return err; if (BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) { insn_idx++; continue; } prev_src_type = &env->insn_aux_data[insn_idx].ptr_type; if (*prev_src_type == NOT_INIT) { /* saw a valid insn * dst_reg = *(u32 *)(src_reg + off) * save type to validate intersecting paths */ *prev_src_type = src_reg_type; } else if (src_reg_type != *prev_src_type && (src_reg_type == PTR_TO_CTX || *prev_src_type == PTR_TO_CTX)) { /* ABuser program is trying to use the same insn * dst_reg = *(u32*) (src_reg + off) * with different pointer types: * src_reg == ctx in one branch and * src_reg == stack|map in some other branch. * Reject it. */ verbose("same insn cannot be used with different pointers\n"); return -EINVAL; } } else if (class == BPF_STX) { enum bpf_reg_type *prev_dst_type, dst_reg_type; if (BPF_MODE(insn->code) == BPF_XADD) { err = check_xadd(env, insn); if (err) return err; insn_idx++; continue; } /* check src1 operand */ err = check_reg_arg(regs, insn->src_reg, SRC_OP); if (err) return err; /* check src2 operand */ err = check_reg_arg(regs, insn->dst_reg, SRC_OP); if (err) return err; dst_reg_type = regs[insn->dst_reg].type; /* check that memory (dst_reg + off) is writeable */ err = check_mem_access(env, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, insn->src_reg); if (err) return err; prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type; if (*prev_dst_type == NOT_INIT) { *prev_dst_type = dst_reg_type; } else if (dst_reg_type != *prev_dst_type && (dst_reg_type == PTR_TO_CTX || *prev_dst_type == PTR_TO_CTX)) { verbose("same insn cannot be used with different pointers\n"); return -EINVAL; } } else if (class == BPF_ST) { if (BPF_MODE(insn->code) != BPF_MEM || insn->src_reg != BPF_REG_0) { verbose("BPF_ST uses reserved fields\n"); return -EINVAL; } /* check src operand */ err = check_reg_arg(regs, insn->dst_reg, SRC_OP); if (err) return err; /* check that memory (dst_reg + off) is writeable */ err = check_mem_access(env, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, -1); if (err) return err; } else if (class == BPF_JMP) { u8 opcode = BPF_OP(insn->code); if (opcode == BPF_CALL) { if (BPF_SRC(insn->code) != BPF_K || insn->off != 0 || insn->src_reg != BPF_REG_0 || insn->dst_reg != BPF_REG_0) { verbose("BPF_CALL uses reserved fields\n"); return -EINVAL; } err = check_call(env, insn->imm, insn_idx); if (err) return err; } else if (opcode == BPF_JA) { if (BPF_SRC(insn->code) != BPF_K || insn->imm != 0 || insn->src_reg != BPF_REG_0 || insn->dst_reg != BPF_REG_0) { verbose("BPF_JA uses reserved fields\n"); return -EINVAL; } insn_idx += insn->off + 1; continue; } else if (opcode == BPF_EXIT) { if (BPF_SRC(insn->code) != BPF_K || insn->imm != 0 || insn->src_reg != BPF_REG_0 || insn->dst_reg != BPF_REG_0) { verbose("BPF_EXIT uses reserved fields\n"); return -EINVAL; } /* eBPF calling convetion is such that R0 is used * to return the value from eBPF program. * Make sure that it's readable at this time * of bpf_exit, which means that program wrote * something into it earlier */ err = check_reg_arg(regs, BPF_REG_0, SRC_OP); if (err) return err; if (is_pointer_value(env, BPF_REG_0)) { verbose("R0 leaks addr as return value\n"); return -EACCES; } process_bpf_exit: insn_idx = pop_stack(env, &prev_insn_idx); if (insn_idx < 0) { break; } else { do_print_state = true; continue; } } else { err = check_cond_jmp_op(env, insn, &insn_idx); if (err) return err; } } else if (class == BPF_LD) { u8 mode = BPF_MODE(insn->code); if (mode == BPF_ABS || mode == BPF_IND) { err = check_ld_abs(env, insn); if (err) return err; } else if (mode == BPF_IMM) { err = check_ld_imm(env, insn); if (err) return err; insn_idx++; } else { verbose("invalid BPF_LD mode\n"); return -EINVAL; } reset_reg_range_values(regs, insn->dst_reg); } else { verbose("unknown insn class %d\n", class); return -EINVAL; } insn_idx++; } verbose("processed %d insns\n", insn_processed); return 0; } static int check_map_prealloc(struct bpf_map *map) { return (map->map_type != BPF_MAP_TYPE_HASH && map->map_type != BPF_MAP_TYPE_PERCPU_HASH && map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) || !(map->map_flags & BPF_F_NO_PREALLOC); } static int check_map_prog_compatibility(struct bpf_map *map, struct bpf_prog *prog) { /* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use * preallocated hash maps, since doing memory allocation * in overflow_handler can crash depending on where nmi got * triggered. */ if (prog->type == BPF_PROG_TYPE_PERF_EVENT) { if (!check_map_prealloc(map)) { verbose("perf_event programs can only use preallocated hash map\n"); return -EINVAL; } if (map->inner_map_meta && !check_map_prealloc(map->inner_map_meta)) { verbose("perf_event programs can only use preallocated inner hash map\n"); return -EINVAL; } } return 0; } /* look for pseudo eBPF instructions that access map FDs and * replace them with actual map pointers */ static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) { struct bpf_insn *insn = env->prog->insnsi; int insn_cnt = env->prog->len; int i, j, err; err = bpf_prog_calc_tag(env->prog); if (err) return err; for (i = 0; i < insn_cnt; i++, insn++) { if (BPF_CLASS(insn->code) == BPF_LDX && (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { verbose("BPF_LDX uses reserved fields\n"); return -EINVAL; } if (BPF_CLASS(insn->code) == BPF_STX && ((BPF_MODE(insn->code) != BPF_MEM && BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { verbose("BPF_STX uses reserved fields\n"); return -EINVAL; } if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { struct bpf_map *map; struct fd f; if (i == insn_cnt - 1 || insn[1].code != 0 || insn[1].dst_reg != 0 || insn[1].src_reg != 0 || insn[1].off != 0) { verbose("invalid bpf_ld_imm64 insn\n"); return -EINVAL; } if (insn->src_reg == 0) /* valid generic load 64-bit imm */ goto next_insn; if (insn->src_reg != BPF_PSEUDO_MAP_FD) { verbose("unrecognized bpf_ld_imm64 insn\n"); return -EINVAL; } f = fdget(insn->imm); map = __bpf_map_get(f); if (IS_ERR(map)) { verbose("fd %d is not pointing to valid bpf_map\n", insn->imm); return PTR_ERR(map); } err = check_map_prog_compatibility(map, env->prog); if (err) { fdput(f); return err; } /* store map pointer inside BPF_LD_IMM64 instruction */ insn[0].imm = (u32) (unsigned long) map; insn[1].imm = ((u64) (unsigned long) map) >> 32; /* check whether we recorded this map already */ for (j = 0; j < env->used_map_cnt; j++) if (env->used_maps[j] == map) { fdput(f); goto next_insn; } if (env->used_map_cnt >= MAX_USED_MAPS) { fdput(f); return -E2BIG; } /* hold the map. If the program is rejected by verifier, * the map will be released by release_maps() or it * will be used by the valid program until it's unloaded * and all maps are released in free_bpf_prog_info() */ map = bpf_map_inc(map, false); if (IS_ERR(map)) { fdput(f); return PTR_ERR(map); } env->used_maps[env->used_map_cnt++] = map; fdput(f); next_insn: insn++; i++; } } /* now all pseudo BPF_LD_IMM64 instructions load valid * 'struct bpf_map *' into a register instead of user map_fd. * These pointers will be used later by verifier to validate map access. */ return 0; } /* drop refcnt of maps used by the rejected program */ static void release_maps(struct bpf_verifier_env *env) { int i; for (i = 0; i < env->used_map_cnt; i++) bpf_map_put(env->used_maps[i]); } /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env) { struct bpf_insn *insn = env->prog->insnsi; int insn_cnt = env->prog->len; int i; for (i = 0; i < insn_cnt; i++, insn++) if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) insn->src_reg = 0; } /* single env->prog->insni[off] instruction was replaced with the range * insni[off, off + cnt). Adjust corresponding insn_aux_data by copying * [0, off) and [off, end) to new locations, so the patched range stays zero */ static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len, u32 off, u32 cnt) { struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data; if (cnt == 1) return 0; new_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog_len); if (!new_data) return -ENOMEM; memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off); memcpy(new_data + off + cnt - 1, old_data + off, sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1)); env->insn_aux_data = new_data; vfree(old_data); return 0; } static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off, const struct bpf_insn *patch, u32 len) { struct bpf_prog *new_prog; new_prog = bpf_patch_insn_single(env->prog, off, patch, len); if (!new_prog) return NULL; if (adjust_insn_aux_data(env, new_prog->len, off, len)) return NULL; return new_prog; } /* convert load instructions that access fields of 'struct __sk_buff' * into sequence of instructions that access fields of 'struct sk_buff' */ static int convert_ctx_accesses(struct bpf_verifier_env *env) { const struct bpf_verifier_ops *ops = env->prog->aux->ops; const int insn_cnt = env->prog->len; struct bpf_insn insn_buf[16], *insn; struct bpf_prog *new_prog; enum bpf_access_type type; int i, cnt, delta = 0; if (ops->gen_prologue) { cnt = ops->gen_prologue(insn_buf, env->seen_direct_write, env->prog); if (cnt >= ARRAY_SIZE(insn_buf)) { verbose("bpf verifier is misconfigured\n"); return -EINVAL; } else if (cnt) { new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt); if (!new_prog) return -ENOMEM; env->prog = new_prog; delta += cnt - 1; } } if (!ops->convert_ctx_access) return 0; insn = env->prog->insnsi + delta; for (i = 0; i < insn_cnt; i++, insn++) { if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) || insn->code == (BPF_LDX | BPF_MEM | BPF_H) || insn->code == (BPF_LDX | BPF_MEM | BPF_W) || insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) type = BPF_READ; else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) || insn->code == (BPF_STX | BPF_MEM | BPF_H) || insn->code == (BPF_STX | BPF_MEM | BPF_W) || insn->code == (BPF_STX | BPF_MEM | BPF_DW)) type = BPF_WRITE; else continue; if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX) continue; cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog); if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { verbose("bpf verifier is misconfigured\n"); return -EINVAL; } new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; /* keep walking new program and skip insns we just inserted */ env->prog = new_prog; insn = new_prog->insnsi + i + delta; } return 0; } /* fixup insn->imm field of bpf_call instructions * and inline eligible helpers as explicit sequence of BPF instructions * * this function is called after eBPF program passed verification */ static int fixup_bpf_calls(struct bpf_verifier_env *env) { struct bpf_prog *prog = env->prog; struct bpf_insn *insn = prog->insnsi; const struct bpf_func_proto *fn; const int insn_cnt = prog->len; struct bpf_insn insn_buf[16]; struct bpf_prog *new_prog; struct bpf_map *map_ptr; int i, cnt, delta = 0; for (i = 0; i < insn_cnt; i++, insn++) { if (insn->code != (BPF_JMP | BPF_CALL)) continue; if (insn->imm == BPF_FUNC_get_route_realm) prog->dst_needed = 1; if (insn->imm == BPF_FUNC_get_prandom_u32) bpf_user_rnd_init_once(); if (insn->imm == BPF_FUNC_tail_call) { /* If we tail call into other programs, we * cannot make any assumptions since they can * be replaced dynamically during runtime in * the program array. */ prog->cb_access = 1; /* mark bpf_tail_call as different opcode to avoid * conditional branch in the interpeter for every normal * call and to prevent accidental JITing by JIT compiler * that doesn't support bpf_tail_call yet */ insn->imm = 0; insn->code |= BPF_X; continue; } if (ebpf_jit_enabled() && insn->imm == BPF_FUNC_map_lookup_elem) { map_ptr = env->insn_aux_data[i + delta].map_ptr; if (map_ptr == BPF_MAP_PTR_POISON || !map_ptr->ops->map_gen_lookup) goto patch_call_imm; cnt = map_ptr->ops->map_gen_lookup(map_ptr, insn_buf); if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { verbose("bpf verifier is misconfigured\n"); return -EINVAL; } new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; /* keep walking new program and skip insns we just inserted */ env->prog = prog = new_prog; insn = new_prog->insnsi + i + delta; continue; } patch_call_imm: fn = prog->aux->ops->get_func_proto(insn->imm); /* all functions that have prototype and verifier allowed * programs to call them, must be real in-kernel functions */ if (!fn->func) { verbose("kernel subsystem misconfigured func %s#%d\n", func_id_name(insn->imm), insn->imm); return -EFAULT; } insn->imm = fn->func - __bpf_call_base; } return 0; } static void free_states(struct bpf_verifier_env *env) { struct bpf_verifier_state_list *sl, *sln; int i; if (!env->explored_states) return; for (i = 0; i < env->prog->len; i++) { sl = env->explored_states[i]; if (sl) while (sl != STATE_LIST_MARK) { sln = sl->next; kfree(sl); sl = sln; } } kfree(env->explored_states); } int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) { char __user *log_ubuf = NULL; struct bpf_verifier_env *env; int ret = -EINVAL; /* 'struct bpf_verifier_env' can be global, but since it's not small, * allocate/free it every time bpf_check() is called */ env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); if (!env) return -ENOMEM; env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * (*prog)->len); ret = -ENOMEM; if (!env->insn_aux_data) goto err_free_env; env->prog = *prog; /* grab the mutex to protect few globals used by verifier */ mutex_lock(&bpf_verifier_lock); if (attr->log_level || attr->log_buf || attr->log_size) { /* user requested verbose verifier output * and supplied buffer to store the verification trace */ log_level = attr->log_level; log_ubuf = (char __user *) (unsigned long) attr->log_buf; log_size = attr->log_size; log_len = 0; ret = -EINVAL; /* log_* values have to be sane */ if (log_size < 128 || log_size > UINT_MAX >> 8 || log_level == 0 || log_ubuf == NULL) goto err_unlock; ret = -ENOMEM; log_buf = vmalloc(log_size); if (!log_buf) goto err_unlock; } else { log_level = 0; } env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT); if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) env->strict_alignment = true; ret = replace_map_fd_with_map_ptr(env); if (ret < 0) goto skip_full_check; env->explored_states = kcalloc(env->prog->len, sizeof(struct bpf_verifier_state_list *), GFP_USER); ret = -ENOMEM; if (!env->explored_states) goto skip_full_check; ret = check_cfg(env); if (ret < 0) goto skip_full_check; env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); ret = do_check(env); skip_full_check: while (pop_stack(env, NULL) >= 0); free_states(env); if (ret == 0) /* program is valid, convert *(u32*)(ctx + off) accesses */ ret = convert_ctx_accesses(env); if (ret == 0) ret = fixup_bpf_calls(env); if (log_level && log_len >= log_size - 1) { BUG_ON(log_len >= log_size); /* verifier log exceeded user supplied buffer */ ret = -ENOSPC; /* fall through to return what was recorded */ } /* copy verifier log back to user space including trailing zero */ if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { ret = -EFAULT; goto free_log_buf; } if (ret == 0 && env->used_map_cnt) { /* if program passed verifier, update used_maps in bpf_prog_info */ env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, sizeof(env->used_maps[0]), GFP_KERNEL); if (!env->prog->aux->used_maps) { ret = -ENOMEM; goto free_log_buf; } memcpy(env->prog->aux->used_maps, env->used_maps, sizeof(env->used_maps[0]) * env->used_map_cnt); env->prog->aux->used_map_cnt = env->used_map_cnt; /* program is valid. Convert pseudo bpf_ld_imm64 into generic * bpf_ld_imm64 instructions */ convert_pseudo_ld_imm64(env); } free_log_buf: if (log_level) vfree(log_buf); if (!env->prog->aux->used_maps) /* if we didn't copy map pointers into bpf_prog_info, release * them now. Otherwise free_bpf_prog_info() will release them. */ release_maps(env); *prog = env->prog; err_unlock: mutex_unlock(&bpf_verifier_lock); vfree(env->insn_aux_data); err_free_env: kfree(env); return ret; } int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, void *priv) { struct bpf_verifier_env *env; int ret; env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); if (!env) return -ENOMEM; env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog->len); ret = -ENOMEM; if (!env->insn_aux_data) goto err_free_env; env->prog = prog; env->analyzer_ops = ops; env->analyzer_priv = priv; /* grab the mutex to protect few globals used by verifier */ mutex_lock(&bpf_verifier_lock); log_level = 0; env->strict_alignment = false; if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) env->strict_alignment = true; env->explored_states = kcalloc(env->prog->len, sizeof(struct bpf_verifier_state_list *), GFP_KERNEL); ret = -ENOMEM; if (!env->explored_states) goto skip_full_check; ret = check_cfg(env); if (ret < 0) goto skip_full_check; env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); ret = do_check(env); skip_full_check: while (pop_stack(env, NULL) >= 0); free_states(env); mutex_unlock(&bpf_verifier_lock); vfree(env->insn_aux_data); err_free_env: kfree(env); return ret; } EXPORT_SYMBOL_GPL(bpf_analyzer);