linux-kernel - Re: WARNING in task_participate_group

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Date:   Mon, 30 Apr 2018 15:22:32 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     syzbot <syzbot+b109633ea805cac54a61@...kaller.appspotmail.com>
Cc:     akpm@...ux-foundation.org, ebiederm@...ssion.com, ldv@...linux.org,
        linux-kernel@...r.kernel.org, linux@...inikbrodowski.net,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: Re: WARNING in task_participate_group_stop (2)

On 04/29, syzbot wrote:
>
> RIP: 0010:task_participate_group_stop+0x205/0x260 kernel/signal.c:351
> RSP: 0018:ffff8801ae7b7880 EFLAGS: 00010093
> RAX: ffff8801d96200c0 RBX: 0000000000000000 RCX: ffffffff81498b5b
> RDX: 0000000000000000 RSI: ffffffff81498c75 RDI: 0000000000000005
> RBP: ffff8801ae7b78a0 R08: ffff8801d96200c0 R09: ffffed0036c48971
> R10: ffffed0036c48971 R11: ffff8801b6244b8b R12: ffff8801d926ecd8
> R13: ffff8801d926ec40 R14: 0000000000040000 R15: dffffc0000000000
>  do_signal_stop+0x502/0xa20 kernel/signal.c:2176
>  get_signal+0x9b4/0x1960 kernel/signal.c:2353
>  do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
>  exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Thanks... I need to think and recall how this code works, but at first glance
zap_other_threads() needs task_clear_jobctl_pending(current).

I am almost sure the warning should go away, but iiuc there are more problems
and it is not clear to me what can we do...

Oleg.