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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 30 Oct 2017 22:20:49 +0300
Message-ID: <CACT4Y+Y-Zi+30FtfNJk5UUeO5RaTs2WNrDz2cKnXbAUyWvfgCQ@mail.gmail.com>
Subject: Re: WARNING in task_participate_group_stop
To:     syzbot 
        <bot+c9f0eb0d2a5576ece331a767528e6b52b4ff1815@syzkaller.appspotmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Arvind Yadav <arvind.yadav.cs@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= <fweisbec@gmail.com>,
        jamie.iles@oracle.com, LKML <linux-kernel@vger.kernel.org>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        mchehab@kernel.org, Ingo Molnar <mingo@kernel.org>,
        mpe@ellerman.id.au, syzkaller-bugs@googlegroups.com,
        Al Viro <viro@zeniv.linux.org.uk>,
        Oleg Nesterov <oleg@redhat.com>
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On Mon, Oct 30, 2017 at 10:12 PM, syzbot
<bot+c9f0eb0d2a5576ece331a767528e6b52b4ff1815@syzkaller.appspotmail.com>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> d95e159cd1da1ed4dbf76bf203e8ffaf231395e4
> git://git.cmpxchg.org/linux-mmots.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers

This also happens on more recent commits, including linux-next
36ef71cae353f88fd6e095e2aaa3e5953af1685d (Oct 19) and upstream
3e0cc09a3a2c40ec1ffb6b4e12da86e98feccb11 (Oct 18).

> WARNING: CPU: 0 PID: 1 at kernel/signal.c:340
> task_participate_group_stop+0x1ce/0x230 kernel/signal.c:340
> Kernel panic - not syncing: panic_on_warn set ...
>
> CPU: 0 PID: 1 Comm: init Not tainted 4.13.0-mm1+ #5
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:16 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:52
>  panic+0x1e4/0x417 kernel/panic.c:181
>  __warn+0x1c4/0x1d9 kernel/panic.c:542
>  report_bug+0x211/0x2d0 lib/bug.c:183
>  fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
>  do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
>  do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
>  do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
>  invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
> RIP: 0010:task_participate_group_stop+0x1ce/0x230 kernel/signal.c:340
> RSP: 0018:ffff8801d9ee77f0 EFLAGS: 00010097
> RAX: ffff8801d9ed8040 RBX: ffff8801d9ed8040 RCX: ffff8801d9edb2c0
> RDX: 0000000000000000 RSI: 0000000000060013 RDI: ffff8801d9ed84d0
> RBP: ffff8801d9ee7808 R08: ffff8801d9ee7180 R09: ffff8801d9ee7178
> R10: ffff8801d9ee70f0 R11: 1ffff1003b3db29b R12: ffff8801d9ee9740
> R13: 0000000000000000 R14: dffffc0000000000 R15: ffff8801d9ed85c8
>  do_signal_stop+0x217/0x900 kernel/signal.c:2042
>  get_signal+0x61c/0x17e0 kernel/signal.c:2297
>  do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:808
>  exit_to_usermode_loop+0x224/0x300 arch/x86/entry/common.c:158
>  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>  syscall_return_slowpath+0x42f/0x500 arch/x86/entry/common.c:266
>  entry_SYSCALL_64_fastpath+0xbc/0xbe
> RIP: 0033:0x7f33f723fdd3
> RSP: 002b:00007fffb5303398 EFLAGS: 00000246 ORIG_RAX: 0000000000000017
> RAX: fffffffffffffdfe RBX: 00007fffb5303540 RCX: 00007f33f723fdd3
> RDX: 0000000000000000 RSI: 00007fffb53036f0 RDI: 000000000000000b
> RBP: 00007fffb53036f0 R08: 00007fffb5303770 R09: 0000000000000001
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00007fffb5303ad0 R14: 0000000000000000 R15: 0000000000000000
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report.
> Once a fix for this bug is committed, please reply to this email with:
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> If it's a one-off invalid bug report, please reply with:
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> Note: if the crash happens again, it will cause creation of a new bug
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>
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