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bpf: Fix kfunc callback register type handling

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The kfunc code to handle KF_ARG_PTR_TO_CALLBACK does not check the reg
type before using reg->subprogno. This can accidently permit invalid
pointers from being passed into callback helpers (e.g. silently from
different paths). Likewise, reg->subprogno from the per-register type
union may not be meaningful either. We need to reject any other type
except PTR_TO_FUNC.

Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Fixes: 5d92ddc3de1b ("bpf: Add callback validation to kfunc verifier logic")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230912233214.1518551-14-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2023-09-13 01:32:10 +02:00 committed by Alexei Starovoitov
parent fd548e1a46
commit 06d686f771
1 changed files with 4 additions and 0 deletions
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4
kernel/bpf/verifier.c
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@ -11407,6 +11407,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
break;
}
case KF_ARG_PTR_TO_CALLBACK:
if (reg->type != PTR_TO_FUNC) {
verbose(env, "arg%d expected pointer to func\n", i);
return -EINVAL;
}
meta->subprogno = reg->subprogno;
break;
case KF_ARG_PTR_TO_REFCOUNTED_KPTR: