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bpf: Make BTF pointer type checking generic

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Perform BTF type checks if the register we're working on contains a BTF
pointer, rather than if the argument is for a BTF pointer. This is easier
to understand, and allows removing the code from the arg_type checking
section of the function.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-6-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer 2020-09-21 13:12:21 +01:00 committed by Alexei Starovoitov
parent 9436ef6e86
commit d7b9454a4f
1 changed files with 20 additions and 18 deletions
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38
kernel/bpf/verifier.c
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@ -4048,27 +4048,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
goto err_type;
}
} else if (arg_type == ARG_PTR_TO_BTF_ID) {
const u32 *btf_id = fn->arg_btf_id[arg];
expected_type = PTR_TO_BTF_ID;
if (type != expected_type)
goto err_type;
if (!btf_id) {
verbose(env, "verifier internal error: missing BTF ID\n");
return -EFAULT;
}
if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, *btf_id)) {
verbose(env, "R%d is of type %s but %s is expected\n",
regno, kernel_type_name(reg->btf_id), kernel_type_name(*btf_id));
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
regno);
return -EACCES;
}
} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
if (meta->func_id == BPF_FUNC_spin_lock) {
if (process_spin_lock(env, regno, true))
@ -4123,6 +4105,26 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
return -EFAULT;
}
if (type == PTR_TO_BTF_ID) {
const u32 *btf_id = fn->arg_btf_id[arg];
if (!btf_id) {
verbose(env, "verifier internal error: missing BTF ID\n");
return -EFAULT;
}
if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, *btf_id)) {
verbose(env, "R%d is of type %s but %s is expected\n",
regno, kernel_type_name(reg->btf_id), kernel_type_name(*btf_id));
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
regno);
return -EACCES;
}
}
if (arg_type == ARG_CONST_MAP_PTR) {
/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
meta->map_ptr = reg->map_ptr;