linux-kernel - Re: [PATCH bpf] bpf: add check for invalid name in btf_name_valid

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Message-ID: <CAADnVQKsZ9zboc4k0mnrwcUv6ioSQ6aBXXC+t+-233n17Vdw-A@mail.gmail.com>
Date: Wed, 28 Aug 2024 19:36:44 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Jeongjun Park <aha310510@...il.com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Eddy Z <eddyz87@...il.com>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf] bpf: add check for invalid name in btf_name_valid_section()

On Fri, Aug 23, 2024 at 3:43 AM Jeongjun Park <aha310510@...il.com> wrote:
>
> If the length of the name string is 1 and the value of name[0] is NULL
> byte, an OOB vulnerability occurs in btf_name_valid_section() and the
> return value is true, so the invalid name passes the check.
>
> To solve this, you need to check if the first position is NULL byte.
>
> Fixes: bd70a8fb7ca4 ("bpf: Allow all printable characters in BTF DATASEC names")
> Signed-off-by: Jeongjun Park <aha310510@...il.com>
> ---
>  kernel/bpf/btf.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 520f49f422fe..5c24ea1a65a4 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -823,6 +823,9 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
>         const char *src = btf_str_by_offset(btf, offset);
>         const char *src_limit;
>
> +       if (!*src)
> +               return false;
> +

We've talked about it. Quote:
"Pls add a selftest that demonstrates the issue
and produce a patch to fix just that."

length == 1 and name[0] = 0 is a hypothesis.
Demonstrate that such a scenario is possible then this patch will be
worth applying.

pw-bot: cr