From: Miklos Szeredi <miklos@szeredi.hu>
To: syzbot <syzbot+d86c4426a01f60feddc7@syzkaller.appspotmail.com>
Cc: bcrl@kvack.org, linux-aio@kvack.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: possible deadlock in free_ioctx_users
Date: Mon, 10 Sep 2018 11:28:48 +0200 [thread overview]
Message-ID: <CAJfpegsqsESUft-azOkirq9363nUXM=Sx4YMX6XVQxquEbjS7Q@mail.gmail.com> (raw)
In-Reply-To: <00000000000024df4605757495a8@google.com>
On Sun, Sep 9, 2018 at 8:41 PM, syzbot
<syzbot+d86c4426a01f60feddc7@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: f8f65382c98a Merge tag 'for-linus' of git://git.kernel.org..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=113260ae400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
> dashboard link: https://syzkaller.appspot.com/bug?extid=d86c4426a01f60feddc7
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=120baa9e400000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13979cbe400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d86c4426a01f60feddc7@syzkaller.appspotmail.com
>
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
>
> ========================================================
> WARNING: possible irq lock inversion dependency detected
> 4.19.0-rc2+ #229 Not tainted
> --------------------------------------------------------
> swapper/0/0 just changed the state of lock:
> 00000000c02bddef (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq
> include/linux/spinlock.h:354 [inline]
> 00000000c02bddef (&(&ctx->ctx_lock)->rlock){..-.}, at:
> free_ioctx_users+0xbc/0x710 fs/aio.c:603
> but this lock took another, SOFTIRQ-unsafe lock in the past:
> (&fiq->waitq){+.+.}
>
>
> and interrupts could create inverse lock ordering between them.
>
>
> other info that might help us debug this:
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&fiq->waitq);
> local_irq_disable();
> lock(&(&ctx->ctx_lock)->rlock);
> lock(&fiq->waitq);
> <Interrupt>
> lock(&(&ctx->ctx_lock)->rlock);
Fuse device doesn't support AIO ops. So false positive, AFAICS.
Thanks,
Miklos
next prev parent reply other threads:[~2018-09-10 9:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-09 18:41 possible deadlock in free_ioctx_users syzbot
2018-09-09 19:11 ` Matthew Wilcox
2018-09-10 9:28 ` Miklos Szeredi [this message]
2018-09-10 9:43 ` Dmitry Vyukov
2018-09-10 9:50 ` Miklos Szeredi
2018-09-10 10:03 ` Dmitry Vyukov
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='CAJfpegsqsESUft-azOkirq9363nUXM=Sx4YMX6XVQxquEbjS7Q@mail.gmail.com' \
--to=miklos@szeredi.hu \
--cc=bcrl@kvack.org \
--cc=linux-aio@kvack.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=syzbot+d86c4426a01f60feddc7@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=viro@zeniv.linux.org.uk \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).