From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-wm0-f46.google.com (mail-wm0-f46.google.com [74.125.82.46])
	by kanga.kvack.org (Postfix) with ESMTP id F33C26B0005
	for <linux-mm@kvack.org>; Tue,  2 Feb 2016 16:30:07 -0500 (EST)
Received: by mail-wm0-f46.google.com with SMTP id l66so42626028wml.0
        for <linux-mm@kvack.org>; Tue, 02 Feb 2016 13:30:07 -0800 (PST)
Received: from mail-wm0-x22f.google.com (mail-wm0-x22f.google.com. [2a00:1450:400c:c09::22f])
        by mx.google.com with ESMTPS id u8si4882618wje.114.2016.02.02.13.30.06
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Tue, 02 Feb 2016 13:30:06 -0800 (PST)
Received: by mail-wm0-x22f.google.com with SMTP id p63so137734252wmp.1
        for <linux-mm@kvack.org>; Tue, 02 Feb 2016 13:30:06 -0800 (PST)
MIME-Version: 1.0
In-Reply-To: <alpine.LNX.2.00.1602022222060.22727@cbobk.fhfr.pm>
References: <CACT4Y+ZqQte+9Uk2FsixfWw7sAR7E5rK_BBr8EJe1M+Sv-i_RQ@mail.gmail.com>
 <alpine.LNX.2.00.1602022204190.22727@cbobk.fhfr.pm> <CACT4Y+YHX-P0X8Y8530FoG2weg39edujD=1JyXZf6c67FM_xzw@mail.gmail.com>
 <CACT4Y+Z=qaJjzOFsksSHur-kED=Jf-JFk_M0jnMNq1y5RG278A@mail.gmail.com> <alpine.LNX.2.00.1602022222060.22727@cbobk.fhfr.pm>
From: Dmitry Vyukov <dvyukov@google.com>
Date: Tue, 2 Feb 2016 22:29:46 +0100
Message-ID: <CACT4Y+ZYGHA5K0JPVOJa2bNiWgQPq1Z3QRjX70LZDH9bME9jnw@mail.gmail.com>
Subject: Re: mm: uninterruptable tasks hanged on mmap_sem
Content-Type: text/plain; charset=UTF-8
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Jiri Kosina <jikos@kernel.org>
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, Feb 2, 2016 at 10:24 PM, Jiri Kosina <jikos@kernel.org> wrote:
> 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).

I have "floppy: fix lock_fdc() signal handling" applied (the final,
second version).
The process is multithreaded and it can well receive SIGKILLs.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>