From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Yonghong Song <yonghong.song@linux.dev>
Cc: bot+bpf-ci@kernel.org, chandna.sahil@gmail.com, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev,
eddyz87@gmail.com, song@kernel.org, john.fastabend@gmail.com,
kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com,
jolsa@kernel.org, bpf@vger.kernel.org,
syzbot+b0cff308140f79a9c4cb@syzkaller.appspotmail.comi,
martin.lau@kernel.org, clm@meta.com, ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next] bpf: use preempt_disable/enable() to protect bpf_bprintf_buffers nesting
Date: Tue, 11 Nov 2025 11:37:05 +0100 [thread overview]
Message-ID: <20251111103705.B_sEhO6r@linutronix.de> (raw)
In-Reply-To: <03bc2787-b5e7-42e7-9812-8c50da912c0b@linux.dev>
On 2025-11-10 09:44:55 [-0800], Yonghong Song wrote:
>
>
> On 11/10/25 5:25 AM, Sebastian Andrzej Siewior wrote:
> > On 2025-11-09 11:44:48 [-0800], Yonghong Song wrote:
> >
> > Could we do this instead?
> > There is __bpf_stream_push_str() => bpf_stream_page_reserve_elem() =>
> > bpf_stream_page_replace() => alloc_pages_nolock().
>
> I would suggest to stick to preempt_disable/enable().
> In the bpf-next (newer change), for function
> bpf_stream_elem_alloc(), kmalloc_nolock() is used
> and no local_lock usage any more.
Okay. This is then basically a revert of the removal of
preempt_disable(). If it doesn't break anything, fine then. I don't have
a strong argument against other than it would impose limitations as
mentioned previously (but this is no longer the case).
Unless it breaks anything, fine by me :)
The correct tags would be:
Reported-by: syzbot+b0cff308140f79a9c4cb@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68f6a4c8.050a0220.1be48.0011.GAE@google.com/
Fixes: 4223bf833c849 ("bpf: Remove preempt_disable in bpf_try_get_buffers")
Sebastian
prev parent reply other threads:[~2025-11-11 10:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-09 17:36 [PATCH bpf-next] bpf: use preempt_disable/enable() to protect bpf_bprintf_buffers nesting Sahil Chandna
2025-11-09 18:07 ` bot+bpf-ci
2025-11-09 19:44 ` Yonghong Song
2025-11-10 13:25 ` Sebastian Andrzej Siewior
2025-11-10 17:44 ` Yonghong Song
2025-11-11 10:37 ` Sebastian Andrzej Siewior [this message]
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