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Date:   Mon, 01 Nov 2021 11:24:34 -0700
From:   syzbot <>
Subject: [syzbot] WARNING in io_poll_task_func


syzbot found the following issue on:

HEAD commit:    bdcc9f6a5682 Add linux-next specific files for 20211029
git tree:       linux-next
console output:
kernel config:
dashboard link:
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:
C reproducer:

The issue was bisected to:

commit 34ced75ca1f63fac6148497971212583aa0f7a87
Author: Xiaoguang Wang <>
Date:   Mon Oct 25 05:38:48 2021 +0000

    io_uring: reduce frequent add_wait_queue() overhead for multi-shot poll request

bisection log:
final oops:
console output:

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Fixes: 34ced75ca1f6 ("io_uring: reduce frequent add_wait_queue() overhead for multi-shot poll request")

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6637 at fs/io_uring.c:1183 req_ref_put_and_test fs/io_uring.c:1183 [inline]
WARNING: CPU: 0 PID: 6637 at fs/io_uring.c:1183 req_ref_put_and_test fs/io_uring.c:1178 [inline]
WARNING: CPU: 0 PID: 6637 at fs/io_uring.c:1183 io_put_req_find_next fs/io_uring.c:2392 [inline]
WARNING: CPU: 0 PID: 6637 at fs/io_uring.c:1183 io_poll_task_func+0x81d/0x9f0 fs/io_uring.c:5412
Modules linked in:
CPU: 0 PID: 6637 Comm: syz-executor446 Not tainted 5.15.0-rc7-next-20211029-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:req_ref_put_and_test fs/io_uring.c:1183 [inline]
RIP: 0010:req_ref_put_and_test fs/io_uring.c:1178 [inline]
RIP: 0010:io_put_req_find_next fs/io_uring.c:2392 [inline]
RIP: 0010:io_poll_task_func+0x81d/0x9f0 fs/io_uring.c:5412
Code: e8 e8 f3 da ff f0 ff 8d 80 00 00 00 0f 94 c3 31 ff 89 de e8 15 33 94 ff 84 db 0f 84 47 f8 ff ff e9 a4 fa ff ff e8 23 2f 94 ff <0f> 0b eb c5 e8 4a f0 da ff e9 0e f8 ff ff 4c 89 f7 e8 0d f0 da ff
RSP: 0018:ffffc90001f8fd98 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 000000000000007f RCX: 0000000000000000
RDX: ffff888016843a80 RSI: ffffffff81e39d0d RDI: 0000000000000003
RBP: ffff88806f8f9640 R08: 000000000000007f R09: ffff88806f8f96c3
R10: ffffffff81e39cd1 R11: 0000000000000000 R12: ffff88806f8f96c0
R13: ffff88806b400000 R14: 0000000000000143 R15: ffff88801c31f3c0
FS:  00007f5ca4281700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc595b2960 CR3: 0000000079b4d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tctx_task_work+0x1b3/0x630 fs/io_uring.c:2207
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 tracehook_notify_signal include/linux/tracehook.h:214 [inline]
 handle_signal_work kernel/entry/common.c:146 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x256/0x290 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
RIP: 0033:0x7f5ca42cfd19
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5ca42812f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: 00000000000002ff RBX: 00007f5ca4357428 RCX: 00007f5ca42cfd19
RDX: 0000000000000000 RSI: 00000000000002ff RDI: 0000000000000003
RBP: 00007f5ca4357420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5ca4325074
R13: 0000000000000000 R14: 00007f5ca4281400 R15: 0000000000022000

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For information about bisection process see:
syzbot can test patches for this issue, for details see:

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