From: Yonghong Song <yonghong.song@linux.dev>
To: Arnaud Lecomte <contact@arnaud-lcm.com>,
syzbot+d1b7fa1092def3628bd7@syzkaller.appspotmail.com
Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, haoluo@google.com,
john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org,
linux-kernel@vger.kernel.org, martin.lau@linux.dev,
netdev@vger.kernel.org, sdf@fomichev.me, song@kernel.org,
syzkaller-bugs@googlegroups.com,
Brahmajit Das <listout@listout.xyz>
Subject: Re: [PATCH] bpf-next: Prevent out of bound buffer write in __bpf_get_stack
Date: Sun, 4 Jan 2026 21:50:04 -0800 [thread overview]
Message-ID: <7a2d0d37-bcca-454f-85c3-063906ecd042@linux.dev> (raw)
In-Reply-To: <20260104205220.980752-1-contact@arnaud-lcm.com>
On 1/4/26 12:52 PM, Arnaud Lecomte wrote:
> Syzkaller reported a KASAN slab-out-of-bounds write in __bpf_get_stack()
> during stack trace copying.
>
> The issue occurs when: the callchain entry (stored as a per-cpu variable)
> grow between collection and buffer copy, causing it to exceed the initially
> calculated buffer size based on max_depth.
>
> The callchain collection intentionally avoids locking for performance
> reasons, but this creates a window where concurrent modifications can
> occur during the copy operation.
>
> To prevent this from happening, we clamp the trace len to the max
> depth initially calculated with the buffer size and the size of
> a trace.
>
> Reported-by: syzbot+d1b7fa1092def3628bd7@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/691231dc.a70a0220.22f260.0101.GAE@google.com/T/
> Fixes: e17d62fedd10 ("bpf: Refactor stack map trace depth calculation into helper function")
> Tested-by: syzbot+d1b7fa1092def3628bd7@syzkaller.appspotmail.com
> Cc: Brahmajit Das <listout@listout.xyz>
> Signed-off-by: Arnaud Lecomte <contact@arnaud-lcm.com>
LGTM.
Acked-by: Yonghong Song <yonghong.song@linux.dev>
next prev parent reply other threads:[~2026-01-05 5:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-04 20:52 Arnaud Lecomte
2026-01-05 5:50 ` Yonghong Song [this message]
2026-01-06 0:51 ` Andrii Nakryiko
2026-01-07 18:08 ` Lecomte, Arnaud
2026-01-07 18:35 ` Lecomte, Arnaud
2026-01-09 19:05 ` Andrii Nakryiko
2026-01-13 21:01 ` Lecomte, Arnaud
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