Re: [syzbot] WARNING in __percpu_ref_exit (2)

[Pavel Begunkov]

On 4/18/21 8:30 PM, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    c98ff1d0 Merge tag 'scsi-fixes' of git://git.kernel.org/pu..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=163d7229d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1c70e618af4c2e92
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6218cb2fae0b2411e9d
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=145cb2b6d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=157b72b1d00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d6218cb2fae0b2411e9d@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 169 at lib/percpu-refcount.c:113 __percpu_ref_exit+0x98/0x100 lib/percpu-refcount.c:113
> Modules linked in:
> CPU: 1 PID: 169 Comm: kworker/u4:3 Not tainted 5.12.0-rc7-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+0x98/0x100 lib/percpu-refcount.c:113
> Code: fd 49 8d 7c 24 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 61 49 83 7c 24 10 00 74 07 e8 a8 4a ab fd <0f> 0b e8 a1 4a ab fd 48 89 ef e8 69 f0 d9 fd 48 89 da 48 b8 00 00
> RSP: 0018:ffffc90001077b48 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff88802d5ca000 RCX: 0000000000000000
> RDX: ffff88801217a1c0 RSI: ffffffff83c7db28 RDI: ffff88801d58f010
> RBP: 0000607f4607bcb8 R08: 0000000000000000 R09: ffffffff8fa9f977
> R10: ffffffff83c7dac8 R11: 0000000000000009 R12: ffff88801d58f000
> R13: 000000010002865e R14: ffff88801d58f000 R15: ffff88802d5ca8b0
> FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000044 CR3: 0000000015c02000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  percpu_ref_exit+0x3b/0x140 lib/percpu-refcount.c:134
>  io_ring_ctx_free fs/io_uring.c:8483 [inline]
>  io_ring_exit_work+0xa64/0x12d0 fs/io_uring.c:8620
>  process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
>  worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
>  kthread+0x3b1/0x4a0 kernel/kthread.c:292
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
> 

#syz test: git://git.kernel.dk/linux-block for-5.13/io_uring

-- 
Pavel Begunkov