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bpf: Set meta->raw_mode for pointers close to use

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If we encounter a pointer to memory, we set meta->raw_mode depending
on the type of memory we point at. What isn't obvious is that this
information is only used when the next memory size argument is
encountered.

Move the assignment closer to where it's used, and add a comment that
explains what is going on.

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/20200921121227.255763-9-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer 2020-09-21 13:12:24 +01:00 committed by Alexei Starovoitov
parent feec704016
commit a2bbe7cc90
1 changed files with 5 additions and 1 deletions
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6
kernel/bpf/verifier.c
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@ -4067,7 +4067,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
type != PTR_TO_RDWR_BUF &&
type != expected_type)
goto err_type;
meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
} else if (arg_type_is_alloc_mem_ptr(arg_type)) {
expected_type = PTR_TO_MEM;
if (register_is_null(reg) &&
@ -4156,6 +4155,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
err = check_helper_mem_access(env, regno,
meta->map_ptr->value_size, false,
meta);
} else if (arg_type_is_mem_ptr(arg_type)) {
/* The access to this pointer is only checked when we hit the
* next is_mem_size argument below.
*/
meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MEM);
} else if (arg_type_is_mem_size(arg_type)) {
bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);