Re: [syzbot] INFO: task hung in io_sq_thread_park (2)

[Pavel Begunkov]

On 7/16/21 11:57 AM, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> WARNING in io_uring_cancel_generic

__arm_poll doesn't remove a second poll entry in case of failed
__io_queue_proc(), it's most likely the cause here.

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

> 
> ctx ffff8880467ee000 submitted 1, dismantled 0, crefs 0, inflight 1, fallbacks 0, poll1 0, poll2 0, tw 0, hash 0, cs 0, issued 1 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 18216 at fs/io_uring.c:9142 io_dump fs/io_uring.c:9142 [inline]
> WARNING: CPU: 0 PID: 18216 at fs/io_uring.c:9142 io_uring_cancel_generic+0x608/0xea0 fs/io_uring.c:9198
> Modules linked in:
> CPU: 0 PID: 18216 Comm: iou-sqp-18211 Not tainted 5.14.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:io_dump fs/io_uring.c:9142 [inline]
> RIP: 0010:io_uring_cancel_generic+0x608/0xea0 fs/io_uring.c:9198
> Code: 48 c1 ea 03 80 3c 02 00 0f 85 d5 02 00 00 48 8b 44 24 10 48 8b a8 98 00 00 00 48 39 6c 24 08 0f 85 02 03 00 00 e8 f8 97 92 ff <0f> 0b e9 af fe ff ff e8 ec 97 92 ff 48 8b 74 24 20 b9 08 00 00 00
> RSP: 0018:ffffc9000afefc40 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff88802a09d4c0 RCX: 0000000000000000
> RDX: ffff88802a09d4c0 RSI: ffffffff81e2f0b8 RDI: ffff8880467ee510
> RBP: ffff8880462fb788 R08: 0000000000000081 R09: 0000000000000000
> R10: ffffffff815d066e R11: 0000000000000000 R12: ffff8880462fa458
> R13: ffffc9000afefd40 R14: 0000000000000001 R15: 0000000000000000
> FS:  00007f9295c2d700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f1c3f1a3000 CR3: 0000000018755000 CR4: 0000000000350ee0
> Call Trace:
>  io_sq_thread+0xaac/0x1250 fs/io_uring.c:6932
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 0 PID: 18216 Comm: iou-sqp-18211 Not tainted 5.14.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
>  panic+0x306/0x73d kernel/panic.c:232
>  __warn.cold+0x35/0x44 kernel/panic.c:606
>  report_bug+0x1bd/0x210 lib/bug.c:199
>  handle_bug+0x3c/0x60 arch/x86/kernel/traps.c:239
>  exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:259
>  asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:566
> RIP: 0010:io_dump fs/io_uring.c:9142 [inline]
> RIP: 0010:io_uring_cancel_generic+0x608/0xea0 fs/io_uring.c:9198
> Code: 48 c1 ea 03 80 3c 02 00 0f 85 d5 02 00 00 48 8b 44 24 10 48 8b a8 98 00 00 00 48 39 6c 24 08 0f 85 02 03 00 00 e8 f8 97 92 ff <0f> 0b e9 af fe ff ff e8 ec 97 92 ff 48 8b 74 24 20 b9 08 00 00 00
> RSP: 0018:ffffc9000afefc40 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff88802a09d4c0 RCX: 0000000000000000
> RDX: ffff88802a09d4c0 RSI: ffffffff81e2f0b8 RDI: ffff8880467ee510
> RBP: ffff8880462fb788 R08: 0000000000000081 R09: 0000000000000000
> R10: ffffffff815d066e R11: 0000000000000000 R12: ffff8880462fa458
> R13: ffffc9000afefd40 R14: 0000000000000001 R15: 0000000000000000
>  io_sq_thread+0xaac/0x1250 fs/io_uring.c:6932
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 
> 
> Tested on:
> 
> commit:         81fee56e io_uring: add syz debug info
> git tree:       https://github.com/isilence/linux.git syztest_sqpoll_hang
> console output: https://syzkaller.appspot.com/x/log.txt?x=12bb485c300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfe2c0e42bc9993d
> dashboard link: https://syzkaller.appspot.com/bug?extid=ac957324022b7132accf
> compiler:       
> 

-- 
Pavel Begunkov