Hello, syzbot found the following issue on: HEAD commit: bdcc9f6a5682 Add linux-next specific files for 20211029 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1413226ab00000 kernel config: https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274 dashboard link: https://syzkaller.appspot.com/bug?extid=30a60157d4ef222fd5e2 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=121ba3e2b00000 The issue was bisected to: commit 34ced75ca1f63fac6148497971212583aa0f7a87 Author: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx> Date: Mon Oct 25 05:38:48 2021 +0000 io_uring: reduce frequent add_wait_queue() overhead for multi-shot poll request bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11d8286ab00000 final oops: https://syzkaller.appspot.com/x/report.txt?x=13d8286ab00000 console output: https://syzkaller.appspot.com/x/log.txt?x=15d8286ab00000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+30a60157d4ef222fd5e2@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 34ced75ca1f6 ("io_uring: reduce frequent add_wait_queue() overhead for multi-shot poll request") ------------[ cut here ]------------ ODEBUG: free active (active state 1) object type: rcu_head hint: 0x0 WARNING: CPU: 0 PID: 6915 at lib/debugobjects.c:505 debug_print_object+0x16e/0x250 lib/debugobjects.c:505 Modules linked in: CPU: 0 PID: 6915 Comm: kworker/0:1 Not tainted 5.15.0-rc7-next-20211029-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events io_fallback_req_func RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:505 Code: ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 00 00 00 48 8b 14 dd 00 4f bf 89 4c 89 ee 48 c7 c7 00 43 bf 89 e8 88 45 2e 05 <0f> 0b 83 05 05 c1 9f 09 01 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e c3 RSP: 0018:ffffc900033a7a98 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000 RDX: ffff88801a799d40 RSI: ffffffff815f3788 RDI: fffff52000674f45 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815ed55e R11: 0000000000000000 R12: ffffffff896d62a0 R13: ffffffff89bf4940 R14: 0000000000000000 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fff9fb60898 CR3: 000000000b48e000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __debug_check_no_obj_freed lib/debugobjects.c:992 [inline] debug_check_no_obj_freed+0x301/0x420 lib/debugobjects.c:1023 slab_free_hook mm/slub.c:1698 [inline] slab_free_freelist_hook+0xeb/0x1c0 mm/slub.c:1749 slab_free mm/slub.c:3513 [inline] kmem_cache_free+0x92/0x5e0 mm/slub.c:3529 __put_task_struct+0x277/0x400 kernel/fork.c:810 put_task_struct_many include/linux/sched/task.h:120 [inline] io_put_task fs/io_uring.c:1773 [inline] __io_free_req+0x2a3/0x3c5 fs/io_uring.c:2037 io_fallback_req_func+0xf9/0x1ae fs/io_uring.c:1335 process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches
