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From: Daniel Borkmann <daniel@iogearbox.net>
To: 임준서 <zirajs7@gmail.com>, "Emil Tsalapatis" <emil@etsalapatis.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Eduard Zingerman <eddyz87@gmail.com>,
	Kumar Kartikeya Dwivedi <memxor@gmail.com>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Stanislav Fomichev <sdf@fomichev.me>, Song Liu <song@kernel.org>,
	Yonghong Song <yonghong.song@linux.dev>,
	Jiri Olsa <jolsa@kernel.org>,
	bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
	Sechang Lim <rhkrqnwk98@gmail.com>
Subject: Re: [PATCH bpf] bpf: Reject negative optlen in cgroup getsockopt hook
Date: Wed, 5 Aug 2026 21:01:46 +0200	[thread overview]
Message-ID: <c1104f11-2444-405e-9fcf-08c2a7bb94cb@iogearbox.net> (raw)
In-Reply-To: <CAB4FuGYv8eUAWzJZB7HbOTktYq-RKB35roAqsT52WxHh_P3VJg@mail.gmail.com>

On 8/1/26 10:26 AM, 임준서 wrote:
> Thanks for the review.
> 
> The reproducer already sets ctx->optlen to a negative value (-11) in
> the cgroup BPF program:
> 
> /* ctx->optlen = -11; */
> BPF_MOV64_IMM(BPF_REG_2, -11),
> BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_2,
>              offsetof(struct bpf_sockopt, optlen)),
> 
> https://gist.github.com/ZirAjs/a177ec6d8f2c8ed7d93edca6313a9255
> 
> The PASS/FAIL output only checks the behavior before and after applying the
> patch. Without the patch, the negative value reaches copy_to_sockptr() and
> triggers the warning. With the patch, getsockopt() rejects it with -EFAULT.
> 
> Would you prefer that I include the reproducer directly in the patch
> submission rather than only linking to the gist?
Yes, please add it as 2nd commit and check git log on how to integrate it
into test_progs (tools/testing/selftests/bpf/) so it can run via CI.

Thanks,
Daniel

      reply	other threads:[~2026-08-05 19:01 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-26  7:01 Junseo Lim
2026-07-29 21:36 ` Emil Tsalapatis
2026-08-01  8:26   ` 임준서
2026-08-05 19:01     ` Daniel Borkmann [this message]

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