From: Eduard Zingerman <eddyz87@gmail.com>
To: sun jian <sun.jian.kdev@gmail.com>, Shung-Hsi Yu <shung-hsi.yu@suse.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Emil Tsalapatis <emil@etsalapatis.com>,
Jiri Olsa <jolsa@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Shuah Khan <shuah@kernel.org>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Matt Mullins <mmullins@mmlx.us>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH bpf v5 2/2] selftests/bpf: Cover negative buffer pointer offsets
Date: Wed, 15 Jul 2026 01:54:37 -0700 [thread overview]
Message-ID: <488c235db713648bb2f5c90e4389c96a97ebcdde.camel@gmail.com> (raw)
In-Reply-To: <CABFUUZFsJsF-C5Z2gb3FkZ7WD=vBavnGdZ7veScP_+dwZLsaMg@mail.gmail.com>
On Wed, 2026-07-15 at 13:26 +0800, sun jian wrote:
[...]
> > Anyway, still recommend adding a regression test that test access to one
> > byte before the start of writable context.
> >
>
> The new tracepoint_writable_reject_negative_const_offset verifier case
> already covers an access before the start of the writable context:
>
> r6 = *(u64 *)(r1 + 0);
> r6 += -8;
> r0 = *(u64 *)(r6 + 0);
>
> Its effective access range is [-8, 0), so it is rejected at load time.
> This is the direct regression test for the negative-start case.
The existing test seem to be sufficient, why would it matter is at
offset -8 or -1 given that the read is appropriately sized?
The added test in tools/testing/selftests/bpf/progs/verifier_raw_tp_writable.c
is redundant given the changes in raw_tp_writable_reject_bad_access.c
but I was going to apply anyway.
next prev parent reply other threads:[~2026-07-15 8:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-14 9:38 [PATCH bpf v5 0/2] bpf: Reject negative const offsets for buffer pointers Sun Jian
2026-07-14 9:38 ` [PATCH bpf v5 1/2] " Sun Jian
2026-07-14 9:38 ` [PATCH bpf v5 2/2] selftests/bpf: Cover negative buffer pointer offsets Sun Jian
2026-07-15 3:02 ` Shung-Hsi Yu
2026-07-15 4:15 ` Shung-Hsi Yu
2026-07-15 4:23 ` Shung-Hsi Yu
2026-07-15 5:26 ` sun jian
2026-07-15 8:54 ` Eduard Zingerman [this message]
2026-07-15 9:16 ` Shung-Hsi Yu
2026-07-15 9:40 ` [PATCH bpf v5 0/2] bpf: Reject negative const offsets for buffer pointers patchwork-bot+netdevbpf
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