From: Al Viro <viro@ZenIV.linux.org.uk>
To: syzbot <syzbot+bacbe5d8791f30c9cee5@syzkaller.appspotmail.com>
Cc: akpm@linux-foundation.org, aneesh.kumar@linux.vnet.ibm.com,
dan.j.williams@intel.com, james.morse@arm.com,
kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, mingo@kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: possible deadlock in get_user_pages_unlocked
Date: Fri, 2 Feb 2018 04:50:20 +0000 [thread overview]
Message-ID: <20180202045020.GF30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <001a113f6344393d89056430347d@google.com>
On Thu, Feb 01, 2018 at 04:58:00PM -0800, syzbot wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> 7109a04eae81c41ed529da9f3c48c3655ccea741 (Thu Feb 1 17:37:30 2018 +0000)
> Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/ide
>
> So far this crash happened 2 times on upstream.
> C reproducer is attached.
Umm... How reproducible that is?
> syzkaller reproducer is attached.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.
Can't reproduce with gcc 5.4.1 (same .config, same C reproducer).
It looks like __get_user_pages_locked() returning with *locked zeroed,
but ->mmap_sem not dropped. I don't see what could've lead to it and
attempts to reproduce had not succeeded so far...
How long does it normally take for lockdep splat to trigger?
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next prev parent reply other threads:[~2018-02-02 4:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-02 0:58 possible deadlock in get_user_pages_unlocked syzbot
2018-02-02 4:50 ` Al Viro [this message]
2018-02-02 5:35 ` Eric Biggers
2018-02-02 5:46 ` Al Viro
2018-02-02 6:20 ` Al Viro
2018-02-02 8:57 ` Dmitry Vyukov
2018-02-10 1:36 ` Al Viro
2018-02-10 3:19 ` Eric Biggers
2018-03-10 4:15 ` Eric Biggers
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