[syzbot] WARNING in percpu_ref_exit (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bf152b0b Merge tag 'for_linus' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14532c1ad00000
kernel config: https://syzkaller.appspot.com/x/.config?x=e2f52d48cfe68458
dashboard link: https://syzkaller.appspot.com/bug?extid=fedc0f6148b1b9a42593
compiler: Debian clang version 11.0.1-2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fedc0f...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 68 at lib/percpu-refcount.c:113 __percpu_ref_exit lib/percpu-refcount.c:113 [inline]
WARNING: CPU: 0 PID: 68 at lib/percpu-refcount.c:113 percpu_ref_exit+0x1e0/0x1f0 lib/percpu-refcount.c:134
Modules linked in:
CPU: 1 PID: 68 Comm: kworker/u4:2 Not tainted 5.12.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound io_ring_exit_work
RIP: 0010:__percpu_ref_exit lib/percpu-refcount.c:113 [inline]
RIP: 0010:percpu_ref_exit+0x1e0/0x1f0 lib/percpu-refcount.c:134
Code: c7 c7 80 67 ce 8c 4c 89 e6 e8 9c 96 84 05 48 8b 3c 24 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d e9 65 8b e8 fd e8 00 68 a5 fd <0f> 0b e9 d0 fe ff ff 66 0f 1f 84 00 00 00 00 00 41 57 41 56 41 55
RSP: 0018:ffffc90000fbfba0 EFLAGS: 00010293
RAX: ffffffff83d35710 RBX: 0000607f46034a90 RCX: ffff88801195b780
RDX: 0000000000000000 RSI: 0000607f46034a90 RDI: 0000000000000000
RBP: ffff8880292ae580 R08: ffffffff83d355a5 R09: fffffbfff1f290ca
R10: fffffbfff1f290ca R11: 0000000000000000 R12: ffff8880292ae590
R13: ffff8880121a6000 R14: 1ffff11002434c00 R15: 1ffff11002434c01
FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32d23000 CR3: 0000000013897000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
io_ring_ctx_free fs/io_uring.c:8419 [inline]
io_ring_exit_work+0x580/0xa90 fs/io_uring.c:8565
process_one_work+0x789/0xfd0 kernel/workqueue.c:2275
worker_thread+0xac1/0x1300 kernel/workqueue.c:2421
kthread+0x39a/0x3c0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.