All of lore.kernel.org
 help / color / mirror / Atom feed
From: Puranjay Mohan <puranjay@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	syzbot <syzbot+97da3d7e0112d59971de@syzkaller.appspotmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Eddy Z <eddyz87@gmail.com>, Hao Luo <haoluo@google.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Jiri Olsa <jolsa@kernel.org>, KP Singh <kpsingh@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-trace-kernel <linux-trace-kernel@vger.kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Matt Bobrowski <mattbobrowski@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Stanislav Fomichev <sdf@fomichev.me>, Song Liu <song@kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Yonghong Song <yonghong.song@linux.dev>
Subject: Re: [syzbot] [bpf?] [trace?] WARNING: locking bug in __lock_task_sighand
Date: Mon, 02 Dec 2024 12:41:53 +0000	[thread overview]
Message-ID: <mb61p8qsymf3i.fsf@kernel.org> (raw)
In-Reply-To: <CAADnVQKdRWA1zG6X4XNwOWtKiUHN-SRREYN_DCNU59LsK8S5LA@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 674 bytes --]

Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> Puranjay, Andrii and All,
>
> looks like if (irqs_disabled()) is not enough.
> Should we change it to preemptible() ?
>
> It will likely make it async all the time,
> but in this it's an ok trade off?
>

Yes, as BPF programs can run in all kinds of contexts.

We should replace 'if (irqs_disabled())' with 'if (!preemptible())'

because the definition is:

#define preemptible()	(preempt_count() == 0 && !irqs_disabled())

and we need if ((preempt_count() != 0) || irqs_disabled()), in both
these cases we want to make it async.

I will try to test the fix as Syzbot has now found a reproducer.

Thanks,
Puranjay

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 255 bytes --]

  reply	other threads:[~2024-12-02 12:42 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-28 13:07 [syzbot] [bpf?] [trace?] WARNING: locking bug in __lock_task_sighand syzbot
2024-11-29 16:47 ` Alexei Starovoitov
2024-12-02 12:41   ` Puranjay Mohan [this message]
2024-12-17 23:49     ` Alexei Starovoitov
2024-12-20 17:30       ` Alexei Starovoitov
2025-01-15 10:38         ` Puranjay Mohan
2025-01-15 11:47           ` syzbot
2024-12-02 10:14 ` syzbot

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=mb61p8qsymf3i.fsf@kernel.org \
    --to=puranjay@kernel.org \
    --cc=alexei.starovoitov@gmail.com \
    --cc=andrii@kernel.org \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=eddyz87@gmail.com \
    --cc=haoluo@google.com \
    --cc=john.fastabend@gmail.com \
    --cc=jolsa@kernel.org \
    --cc=kpsingh@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-trace-kernel@vger.kernel.org \
    --cc=martin.lau@linux.dev \
    --cc=mathieu.desnoyers@efficios.com \
    --cc=mattbobrowski@google.com \
    --cc=mhiramat@kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=sdf@fomichev.me \
    --cc=song@kernel.org \
    --cc=syzbot+97da3d7e0112d59971de@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    --cc=yonghong.song@linux.dev \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.