[syzbot] WARNING in signalfd_cleanup

[syzbot]

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

The issue was bisected to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet <edum...@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+5426c7...@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.
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syzbot will keep track of this issue. See:
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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

[Eric Dumazet]

On Wed, Jan 5, 2022 at 7:37 AM syzbot
<syzbot+5426c7...@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.

[Eric Biggers]

[+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...@kernel.dk/

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[Pavel Begunkov]

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...@kernel.dk/

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

--
Pavel Begunkov

[Pavel Begunkov]

On 1/5/22 17:37, Pavel Begunkov wrote:
> 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...@kernel.dk/
>
> We've got some fixing and groundwork done, but not POLLFREE yet.
> Great to have a repro, thanks

#syz test: https://github.com/isilence/linux.git pollfree_test1

Almost identical to how Eric did it for aio, let's try it out

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+5426c7...@syzkaller.appspotmail.com

Tested on:

commit: 59fb37ef io_uring: pollfree
git tree: https://github.com/isilence/linux.git pollfree_test1
kernel config: https://syzkaller.appspot.com/x/.config?x=d2aaa2946b030309

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

Note: testing is done by a robot and is best-effort only.