From: Dmitry Vyukov <dvyukov@google.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: syzbot <syzbot+d86c4426a01f60feddc7@syzkaller.appspotmail.com>,
bcrl <bcrl@kvack.org>, linux-aio <linux-aio@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <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 11:43:31 +0200 [thread overview]
Message-ID: <CACT4Y+bhGKrHk_BB4g9nDtRYD9VaaPyBTRxTo98r1BufAh6Z8A@mail.gmail.com> (raw)
In-Reply-To: <CAJfpegsqsESUft-azOkirq9363nUXM=Sx4YMX6XVQxquEbjS7Q@mail.gmail.com>
On Mon, Sep 10, 2018 at 11:28 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> 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.
Hi Miklos,
We still need to annotate this. How?
next prev parent reply other threads:[~2018-09-10 14:37 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
2018-09-10 9:43 ` Dmitry Vyukov [this message]
2018-09-10 9:50 ` Miklos Szeredi
2018-09-10 10:03 ` Dmitry Vyukov
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