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Date: Tue, 2 Feb 2016 22:24:04 +0100 (CET)
From: Jiri Kosina <jikos@kernel.org>
Subject: Re: mm: uninterruptable tasks hanged on mmap_sem
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To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Oleg Nesterov <oleg@redhat.com>, Konstantin Khlebnikov <koct9i@gmail.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Takashi Iwai <tiwai@suse.de>, syzkaller <syzkaller@googlegroups.com>, Kostya Serebryany <kcc@google.com>, Alexander Potapenko <glider@google.com>, Sasha Levin <sasha.levin@oracle.com>

On Tue, 2 Feb 2016, Dmitry Vyukov wrote:

> Original log from fuzzer contained the following WARNING in
> mm/rmap.c:412. But when I tried to reproduce it, I hit these hanged
> processes instead. I can't reliably detect what program triggered
> what. So it may be related, or maybe a separate issue.
> 
> ------------[ cut here ]------------
> kernel BUG at mm/rmap.c:412!

Are you by any chance in this test sending signals to the fuzzer?

If so, the bug I just fixed in floppy driver can cause all kinds of memory 
corruptions in case you're running multithreaded accessess to /dev/fd0 and 
sending singals to the threads that are trying to access /dev/fd0 at the 
same time.

Could you please double check that the other floppy fix I've sent you a 
couple days ago doesn't fix this as well? (this test makes sense only if 
signals are involved though).

Thanks,

-- 
Jiri Kosina
SUSE Labs

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