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bpf: Require ARG_PTR_TO_MEM with memory flag

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Add check to ensure that ARG_PTR_TO_MEM is used with either MEM_WRITE or
MEM_RDONLY.

Using ARG_PTR_TO_MEM alone without flags does not make sense because:

- If the helper does not change the argument, missing MEM_RDONLY causes the
verifier to incorrectly reject a read-only buffer.
- If the helper does change the argument, missing MEM_WRITE causes the
verifier to incorrectly assume the memory is unchanged, leading to errors
in code optimization.

Co-developed-by: Shuran Liu <electronlsr@gmail.com>
Signed-off-by: Shuran Liu <electronlsr@gmail.com>
Co-developed-by: Peili Gao <gplhust955@gmail.com>
Signed-off-by: Peili Gao <gplhust955@gmail.com>
Co-developed-by: Haoran Ni <haoran.ni.cs@gmail.com>
Signed-off-by: Haoran Ni <haoran.ni.cs@gmail.com>
Signed-off-by: Zesen Liu <ftyghome@gmail.com>
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260120-helper_proto-v3-2-27b0180b4e77@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Zesen Liu 2026-01-20 16:28:47 +08:00 committed by Alexei Starovoitov
parent 802eef5afb
commit ed4724212f
1 changed files with 17 additions and 0 deletions
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17
kernel/bpf/verifier.c
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@ -10441,10 +10441,27 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn)
return true;
}
static bool check_mem_arg_rw_flag_ok(const struct bpf_func_proto *fn)
{
int i;
for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) {
enum bpf_arg_type arg_type = fn->arg_type[i];
if (base_type(arg_type) != ARG_PTR_TO_MEM)
continue;
if (!(arg_type & (MEM_WRITE | MEM_RDONLY)))
return false;
}
return true;
}
static int check_func_proto(const struct bpf_func_proto *fn)
{
return check_raw_mode_ok(fn) &&
check_arg_pair_ok(fn) &&
check_mem_arg_rw_flag_ok(fn) &&
check_btf_id_ok(fn) ? 0 : -EINVAL;
}