Re: WARNING in io_uring_cancel_task_requests

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    d03154e8 Add linux-next specific files for 20210128
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12e976e8d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6953ffb584722a1
dashboard link: https://syzkaller.appspot.com/bug?extid=3e3d9bd0c6ce9efbc3ef
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=163f0fc8d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3e3d9bd0c6ce9efbc3ef@xxxxxxxxxxxxxxxxxxxxxxxxx

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WARNING: CPU: 0 PID: 11283 at fs/io_uring.c:9042 io_uring_cancel_task_requests+0xe55/0x10c0 fs/io_uring.c:9042
Modules linked in:
CPU: 0 PID: 11283 Comm: syz-executor.4 Not tainted 5.11.0-rc5-next-20210128-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:io_uring_cancel_task_requests+0xe55/0x10c0 fs/io_uring.c:9042
Code: 00 00 e9 1c fe ff ff 48 8b 7c 24 18 e8 f4 b4 da ff e9 f2 fc ff ff 48 8b 7c 24 18 e8 e5 b4 da ff e9 64 f2 ff ff e8 eb 16 97 ff <0f> 0b e9 ed f2 ff ff e8 df b4 da ff e9 c8 f5 ff ff 4c 89 ef e8 52
RSP: 0018:ffffc90002b8f950 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88801849d000 RCX: 0000000000000000
RDX: ffff8880277d0000 RSI: ffffffff81dbfe65 RDI: ffff88801849d0d0
RBP: ffff88801849d0e8 R08: 0000000000000000 R09: ffff8880277d0007
R10: ffffffff81dbf0df R11: 0000000000000000 R12: ffff88801849d000
R13: ffff8880277d0000 R14: ffff88803d874400 R15: ffff888028d0e018
FS:  0000000000000000(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f40244ffdb8 CR3: 0000000019c59000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 io_uring_flush+0x47b/0x6e0 fs/io_uring.c:9227
 filp_close+0xb4/0x170 fs/open.c:1295
 close_files fs/file.c:403 [inline]
 put_files_struct fs/file.c:418 [inline]
 put_files_struct+0x1cc/0x350 fs/file.c:415
 exit_files+0x7e/0xa0 fs/file.c:435
 do_exit+0xc22/0x2ae0 kernel/exit.c:820
 do_group_exit+0x125/0x310 kernel/exit.c:922
 get_signal+0x427/0x20f0 kernel/signal.c:2773
 arch_do_signal_or_restart+0x2a8/0x1eb0 arch/x86/kernel/signal.c:811
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x148/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e219
Code: Unable to access opcode bytes at RIP 0x45e1ef.
RSP: 002b:00007f0355608cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000119bf88 RCX: 000000000045e219
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000119bf88
RBP: 000000000119bf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119bf8c
R13: 00007fff5130821f R14: 00007f03556099c0 R15: 000000000119bf8c