Re: [syzbot] WARNING in signalfd_cleanup

[Pavel Begunkov <asml.silence@gmail.com>]

On 1/5/22 15:52, Eric Biggers wrote:
> [+io_uring list and maintainers]
> 
> This appears to be the known bug in io_uring where it doesn't POLLFREE
> notifications.  See previous discussion:
> https://lore.kernel.org/all/4a472e72-d527-db79-d46e-efa9d4cad5bb@kernel.dk/

We've got some fixing and groundwork done, but not POLLFREE yet.
Great to have a repro, thanks


> On Wed, Jan 05, 2022 at 07:42:10AM -0800, 'Eric Dumazet' via syzkaller-bugs wrote:
>> On Wed, Jan 5, 2022 at 7:37 AM syzbot
>> <syzbot+5426c7ed6868c705ca14@syzkaller.appspotmail.com> wrote:
>>>
>>> Hello,
>>>
>>> syzbot found the following issue on:
>>>
>>> HEAD commit:    6b8d4927540e Add linux-next specific files for 20220104
>>> git tree:       linux-next
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=159d88e3b00000
>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=45c9bbbf2ae8e3d3
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=5426c7ed6868c705ca14
>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=117be65db00000
>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15a75c8db00000
>>>
>>
>> C repro looks legit, point to an io_uring issue.
>>
>>> The issue was bisected to:
>>
>> Please ignore the bisection.
>>
>>>
>>> commit e4b8954074f6d0db01c8c97d338a67f9389c042f
>>> Author: Eric Dumazet <edumazet@google.com>
>>> Date:   Tue Dec 7 01:30:37 2021 +0000
>>>
>>>      netlink: add net device refcount tracker to struct ethnl_req_info
>>>
>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12bca4e3b00000
>>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=11bca4e3b00000
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=16bca4e3b00000
>>>
>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>> Reported-by: syzbot+5426c7ed6868c705ca14@syzkaller.appspotmail.com
>>> Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")
>>>
>>> ------------[ cut here ]------------
>>> WARNING: CPU: 0 PID: 3604 at kernel/sched/wait.c:245 __wake_up_pollfree+0x40/0x50 kernel/sched/wait.c:246
>>> Modules linked in:
>>> CPU: 0 PID: 3604 Comm: syz-executor714 Not tainted 5.16.0-rc8-next-20220104-syzkaller #0
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>>> RIP: 0010:__wake_up_pollfree+0x40/0x50 kernel/sched/wait.c:245
>>> Code: f3 ff ff 48 8d 6b 40 48 b8 00 00 00 00 00 fc ff df 48 89 ea 48 c1 ea 03 80 3c 02 00 75 11 48 8b 43 40 48 39 c5 75 03 5b 5d c3 <0f> 0b 5b 5d c3 48 89 ef e8 13 d8 69 00 eb e5 cc 48 c1 e7 06 48 63
>>> RSP: 0018:ffffc90001aaf9f8 EFLAGS: 00010083
>>> RAX: ffff88801cd623f0 RBX: ffff88801bec8048 RCX: 0000000000000000
>>> RDX: 1ffff110037d9011 RSI: 0000000000000004 RDI: 0000000000000001
>>> RBP: ffff88801bec8088 R08: 0000000000000000 R09: ffff88801bec804b
>>> R10: ffffed10037d9009 R11: 0000000000000000 R12: ffff88801bec8040
>>> R13: ffff88801e029d40 R14: dffffc0000000000 R15: ffff88807eb50000
>>> FS:  00005555573ad300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 00000000200000c0 CR3: 000000001e5e4000 CR4: 00000000003506f0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>> Call Trace:
>>>   <TASK>
>>>   wake_up_pollfree include/linux/wait.h:271 [inline]
>>>   signalfd_cleanup+0x42/0x60 fs/signalfd.c:38
>>>   __cleanup_sighand kernel/fork.c:1596 [inline]
>>>   __cleanup_sighand+0x72/0xb0 kernel/fork.c:1593
>>>   __exit_signal kernel/exit.c:159 [inline]
>>>   release_task+0xc02/0x17e0 kernel/exit.c:200
>>>   wait_task_zombie kernel/exit.c:1117 [inline]
>>>   wait_consider_task+0x2fa6/0x3b80 kernel/exit.c:1344
>>>   do_wait_thread kernel/exit.c:1407 [inline]
>>>   do_wait+0x6ca/0xce0 kernel/exit.c:1524
>>>   kernel_wait4+0x14c/0x260 kernel/exit.c:1687
>>>   __do_sys_wait4+0x13f/0x150 kernel/exit.c:1715
>>>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>>   do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>>>   entry_SYSCALL_64_after_hwframe+0x44/0xae
>>> RIP: 0033:0x7facd6682386
>>> Code: 0f 1f 40 00 31 c9 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 49 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 3d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 90 48 83 ec 28 89 54 24 14 48 89 74 24
>>> RSP: 002b:00007ffdb91adef8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
>>> RAX: ffffffffffffffda RBX: 000000000000c646 RCX: 00007facd6682386
>>> RDX: 0000000040000001 RSI: 00007ffdb91adf14 RDI: 00000000ffffffff
>>> RBP: 0000000000000f17 R08: 0000000000000032 R09: 00007ffdb91ec080
>>> R10: 0000000000000000 R11: 0000000000000246 R12: 431bde82d7b634db
>>> R13: 00007ffdb91adf14 R14: 0000000000000000 R15: 0000000000000000
>>>   </TASK>
>>>
>>>
>>> ---
>>> This report is generated by a bot. It may contain errors.
>>> See https://goo.gl/tpsmEJ for more information about syzbot.
>>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>>>
>>> syzbot will keep track of this issue. See:
>>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>>> syzbot can test patches for this issue, for details see:
>>> https://goo.gl/tpsmEJ#testing-patches
>>
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-- 
Pavel Begunkov