======================================================
WARNING: possible circular locking dependency detected
5.15.0-syzkaller #0 Not tainted
------------------------------------------------------
systemd-udevd/20751 is trying to acquire lock:
ffff88807cd3a938 ((wq_completion)loop2){+.+.}-{0:0}, at: flush_workqueue+0xe1/0x15b0 kernel/workqueue.c:2815

but task is already holding lock:
ffff88801a0d6360 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x7a/0x1070 drivers/block/loop.c:1106

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (&lo->lo_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:607 [inline]
       __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
       lo_open+0x75/0x120 drivers/block/loop.c:1733
       blkdev_get_whole+0x99/0x2d0 block/bdev.c:671
       blkdev_get_by_dev.part.0+0x354/0xb50 block/bdev.c:826
       blkdev_get_by_dev+0x6b/0x80 block/bdev.c:859
       blkdev_open+0x154/0x2e0 block/fops.c:501
       do_dentry_open+0x4c8/0x1250 fs/open.c:822
       do_open fs/namei.c:3426 [inline]
       path_openat+0x1cad/0x2750 fs/namei.c:3559
       do_filp_open+0x1aa/0x400 fs/namei.c:3586
       do_sys_openat2+0x16d/0x4d0 fs/open.c:1212
       do_sys_open fs/open.c:1228 [inline]
       __do_sys_open fs/open.c:1236 [inline]
       __se_sys_open fs/open.c:1232 [inline]
       __x64_sys_open+0x119/0x1c0 fs/open.c:1232
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #6 (&disk->open_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:607 [inline]
       __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
       blkdev_get_by_dev.part.0+0x24e/0xb50 block/bdev.c:819
       blkdev_get_by_dev+0x6b/0x80 block/bdev.c:859
       swsusp_check+0x97/0x2f0 kernel/power/swap.c:1520
       software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:979
       software_resume kernel/power/hibernate.c:86 [inline]
       resume_store+0x161/0x190 kernel/power/hibernate.c:1181
       kobj_attr_store+0x50/0x80 lib/kobject.c:856
       sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
       kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2162 [inline]
       new_sync_write+0x429/0x660 fs/read_write.c:503
       vfs_write+0x7cd/0xae0 fs/read_write.c:590
       ksys_write+0x12d/0x250 fs/read_write.c:643
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #5 (system_transition_mutex/1){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:607 [inline]
       __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
       software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:934
       software_resume kernel/power/hibernate.c:86 [inline]
       resume_store+0x161/0x190 kernel/power/hibernate.c:1181
       kobj_attr_store+0x50/0x80 lib/kobject.c:856
       sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
       kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2162 [inline]
       new_sync_write+0x429/0x660 fs/read_write.c:503
       vfs_write+0x7cd/0xae0 fs/read_write.c:590
       ksys_write+0x12d/0x250 fs/read_write.c:643
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #4 (&of->mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:607 [inline]
       __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
       kernfs_seq_start+0x4b/0x260 fs/kernfs/file.c:112
       seq_read_iter+0x2c7/0x1240 fs/seq_file.c:225
       kernfs_fop_read_iter+0x44f/0x5f0 fs/kernfs/file.c:241
       call_read_iter include/linux/fs.h:2156 [inline]
       new_sync_read+0x421/0x6e0 fs/read_write.c:400
       vfs_read+0x35c/0x600 fs/read_write.c:481
       ksys_read+0x12d/0x250 fs/read_write.c:619
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #3 (&p->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:607 [inline]
       __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
       seq_read_iter+0xdf/0x1240 fs/seq_file.c:182
       call_read_iter include/linux/fs.h:2156 [inline]
       generic_file_splice_read+0x453/0x6d0 fs/splice.c:311
       do_splice_to+0x1bf/0x250 fs/splice.c:796
       splice_direct_to_actor+0x2c2/0x8c0 fs/splice.c:870
       do_splice_direct+0x1b3/0x280 fs/splice.c:979
       do_sendfile+0xaf2/0x1250 fs/read_write.c:1245
       __do_sys_sendfile64 fs/read_write.c:1310 [inline]
       __se_sys_sendfile64 fs/read_write.c:1296 [inline]
       __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1296
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #2 (sb_writers#3){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1810 [inline]
       sb_start_write include/linux/fs.h:1880 [inline]
       file_start_write include/linux/fs.h:3009 [inline]
       lo_write_bvec drivers/block/loop.c:242 [inline]
       lo_write_simple drivers/block/loop.c:265 [inline]
       do_req_filebacked drivers/block/loop.c:494 [inline]
       loop_handle_cmd drivers/block/loop.c:1857 [inline]
       loop_process_work+0x1499/0x1db0 drivers/block/loop.c:1897
       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

-> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
       process_one_work+0x921/0x1690 kernel/workqueue.c:2274
       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

-> #0 ((wq_completion)loop2){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3066 [inline]
       check_prevs_add kernel/locking/lockdep.c:3189 [inline]
       validate_chain kernel/locking/lockdep.c:3804 [inline]
       __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5030
       lock_acquire kernel/locking/lockdep.c:5640 [inline]
       lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5605
       flush_workqueue+0x110/0x15b0 kernel/workqueue.c:2818
       drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2983
       destroy_workqueue+0x71/0x800 kernel/workqueue.c:4420
       __loop_clr_fd+0x1de/0x1070 drivers/block/loop.c:1124
       lo_release+0x1ac/0x1f0 drivers/block/loop.c:1761
       blkdev_put_whole block/bdev.c:694 [inline]
       blkdev_put+0x2fb/0x9e0 block/bdev.c:956
       blkdev_close+0x6a/0x80 block/fops.c:515
       __fput+0x286/0x9f0 fs/file_table.c:280
       task_work_run+0xdd/0x1a0 kernel/task_work.c:164
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
       exit_to_user_mode_prepare+0x27e/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
       entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
  (wq_completion)loop2 --> &disk->open_mutex --> &lo->lo_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&lo->lo_mutex);
                               lock(&disk->open_mutex);
                               lock(&lo->lo_mutex);
  lock((wq_completion)loop2);

 *** DEADLOCK ***

2 locks held by systemd-udevd/20751:
 #0: ffff88801a272918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0x97/0x9e0 block/bdev.c:914
 #1: ffff88801a0d6360 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x7a/0x1070 drivers/block/loop.c:1106

stack backtrace:
CPU: 1 PID: 20751 Comm: systemd-udevd Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2146
 check_prev_add kernel/locking/lockdep.c:3066 [inline]
 check_prevs_add kernel/locking/lockdep.c:3189 [inline]
 validate_chain kernel/locking/lockdep.c:3804 [inline]
 __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5030
 lock_acquire kernel/locking/lockdep.c:5640 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5605
 flush_workqueue+0x110/0x15b0 kernel/workqueue.c:2818
 drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2983
 destroy_workqueue+0x71/0x800 kernel/workqueue.c:4420
 __loop_clr_fd+0x1de/0x1070 drivers/block/loop.c:1124
 lo_release+0x1ac/0x1f0 drivers/block/loop.c:1761
 blkdev_put_whole block/bdev.c:694 [inline]
 blkdev_put+0x2fb/0x9e0 block/bdev.c:956
 blkdev_close+0x6a/0x80 block/fops.c:515
 __fput+0x286/0x9f0 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x27e/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
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f0cb11e1270
Code: 73 01 c3 48 8b 0d 38 7d 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 59 c1 20 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ee fb ff ff 48 89 04 24
RSP: 002b:00007ffc8c96b968 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f0cb11e1270
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00007f0cb209b710 R08: 0000562980e90030 R09: 0000562980e8fe00
R10: 00007f0cb209b8c0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000562980e89850 R14: 0000000000000003 R15: 000000000000000e
 </TASK>