======================================================
WARNING: possible circular locking dependency detected
5.15.186-syzkaller #0 Not tainted
------------------------------------------------------
udevd/4026 is trying to acquire lock:
ffff0000dbdbf138 ((wq_completion)loop5){+.+.}-{0:0}, at: flush_workqueue+0xf4/0x1024 kernel/workqueue.c:2827

but task is already holding lock:
ffff0000cc100468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xa4/0x978 drivers/block/loop.c:1366

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&lo->lo_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_killable_nested+0xac/0x11c kernel/locking/mutex.c:758
       lo_open+0x68/0x148 drivers/block/loop.c:2056
       blkdev_get_whole+0x94/0x344 block/bdev.c:669
       blkdev_get_by_dev+0x224/0x874 block/bdev.c:827
       blkdev_open+0x108/0x27c block/fops.c:466
       do_dentry_open+0x760/0xebc fs/open.c:826
       vfs_open+0x7c/0x90 fs/open.c:956
       do_open fs/namei.c:3608 [inline]
       path_openat+0x1f80/0x26e4 fs/namei.c:3742
       do_filp_open+0x164/0x330 fs/namei.c:3769
       do_sys_openat2+0x128/0x3d8 fs/open.c:1253
       do_sys_open fs/open.c:1269 [inline]
       __do_sys_openat fs/open.c:1285 [inline]
       __se_sys_openat fs/open.c:1280 [inline]
       __arm64_sys_openat+0x120/0x154 fs/open.c:1280
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #8 (&disk->open_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       bd_register_pending_holders+0x40/0x2d0 block/holder.c:161
       device_add_disk+0x454/0xad0 block/genhd.c:486
       add_disk include/linux/genhd.h:200 [inline]
       md_alloc+0x6a0/0xa54 drivers/md/md.c:5782
       md_probe+0x6c/0x88 drivers/md/md.c:5812
       blk_probe_dev block/genhd.c:685 [inline]
       blk_request_module+0x274/0x29c block/genhd.c:-1
       blkdev_get_no_open+0x4c/0x1b4 block/bdev.c:740
       blkdev_get_by_dev+0x84/0x874 block/bdev.c:807
       swsusp_check+0xa0/0x2b0 kernel/power/swap.c:1526
       software_resume+0xe8/0x408 kernel/power/hibernate.c:982
       resume_store+0xe4/0x134 kernel/power/hibernate.c:1184
       kobj_attr_store+0x6c/0x90 lib/kobject.c:864
       sysfs_kf_write+0x1f8/0x278 fs/sysfs/file.c:139
       kernfs_fop_write_iter+0x320/0x478 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x7c8/0xa2c fs/read_write.c:594
       ksys_write+0x120/0x210 fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #7 (disks_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       md_alloc+0x60/0xa54 drivers/md/md.c:5723
       md_probe+0x6c/0x88 drivers/md/md.c:5812
       blk_probe_dev block/genhd.c:685 [inline]
       blk_request_module+0x274/0x29c block/genhd.c:-1
       blkdev_get_no_open+0x4c/0x1b4 block/bdev.c:740
       blkdev_get_by_dev+0x84/0x874 block/bdev.c:807
       swsusp_check+0xa0/0x2b0 kernel/power/swap.c:1526
       software_resume+0xe8/0x408 kernel/power/hibernate.c:982
       resume_store+0xe4/0x134 kernel/power/hibernate.c:1184
       kobj_attr_store+0x6c/0x90 lib/kobject.c:864
       sysfs_kf_write+0x1f8/0x278 fs/sysfs/file.c:139
       kernfs_fop_write_iter+0x320/0x478 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x7c8/0xa2c fs/read_write.c:594
       ksys_write+0x120/0x210 fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #6 (major_names_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       blk_probe_dev block/genhd.c:682 [inline]
       blk_request_module+0x40/0x29c block/genhd.c:698
       blkdev_get_no_open+0x4c/0x1b4 block/bdev.c:740
       blkdev_get_by_dev+0x84/0x874 block/bdev.c:807
       swsusp_check+0xa0/0x2b0 kernel/power/swap.c:1526
       software_resume+0xe8/0x408 kernel/power/hibernate.c:982
       resume_store+0xe4/0x134 kernel/power/hibernate.c:1184
       kobj_attr_store+0x6c/0x90 lib/kobject.c:864
       sysfs_kf_write+0x1f8/0x278 fs/sysfs/file.c:139
       kernfs_fop_write_iter+0x320/0x478 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x7c8/0xa2c fs/read_write.c:594
       ksys_write+0x120/0x210 fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #5 (system_transition_mutex/1){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       software_resume+0x9c/0x408 kernel/power/hibernate.c:937
       resume_store+0xe4/0x134 kernel/power/hibernate.c:1184
       kobj_attr_store+0x6c/0x90 lib/kobject.c:864
       sysfs_kf_write+0x1f8/0x278 fs/sysfs/file.c:139
       kernfs_fop_write_iter+0x320/0x478 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x7c8/0xa2c fs/read_write.c:594
       ksys_write+0x120/0x210 fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #4 (&of->mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       kernfs_seq_start+0x58/0x390 fs/kernfs/file.c:112
       seq_read_iter+0x354/0xc00 fs/seq_file.c:225
       kernfs_fop_read_iter+0x140/0x500 fs/kernfs/file.c:241
       call_read_iter include/linux/fs.h:2166 [inline]
       new_sync_read fs/read_write.c:404 [inline]
       vfs_read+0x7c4/0xa10 fs/read_write.c:485
       ksys_read+0x120/0x210 fs/read_write.c:623
       __do_sys_read fs/read_write.c:633 [inline]
       __se_sys_read fs/read_write.c:631 [inline]
       __arm64_sys_read+0x7c/0x90 fs/read_write.c:631
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #3 (&p->lock){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       seq_read_iter+0xa8/0xc00 fs/seq_file.c:182
       call_read_iter include/linux/fs.h:2166 [inline]
       generic_file_splice_read+0x310/0x4cc fs/splice.c:311
       do_splice_to fs/splice.c:796 [inline]
       splice_direct_to_actor+0x334/0x950 fs/splice.c:870
       do_splice_direct+0x158/0x248 fs/splice.c:979
       do_sendfile+0x458/0xc88 fs/read_write.c:1249
       __do_sys_sendfile64 fs/read_write.c:1317 [inline]
       __se_sys_sendfile64 fs/read_write.c:1303 [inline]
       __arm64_sys_sendfile64+0x130/0x3b0 fs/read_write.c:1303
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #2 (sb_writers#5){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_write include/linux/fs.h:1881 [inline]
       file_start_write include/linux/fs.h:3042 [inline]
       lo_write_bvec+0x200/0xa24 drivers/block/loop.c:315
       lo_write_simple drivers/block/loop.c:338 [inline]
       do_req_filebacked drivers/block/loop.c:656 [inline]
       loop_handle_cmd drivers/block/loop.c:2235 [inline]
       loop_process_work+0x1a18/0x20d0 drivers/block/loop.c:2275
       loop_rootcg_workfn+0x28/0x38 drivers/block/loop.c:2306
       process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
       worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
       kthread+0x374/0x454 kernel/kthread.c:334
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855

-> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
       process_one_work+0x6e0/0x1140 kernel/workqueue.c:2286
       worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
       kthread+0x374/0x454 kernel/kthread.c:334
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855

-> #0 ((wq_completion)loop5){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
       lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
       flush_workqueue+0x11c/0x1024 kernel/workqueue.c:2830
       drain_workqueue+0xa4/0x310 kernel/workqueue.c:2995
       destroy_workqueue+0x80/0x9ac kernel/workqueue.c:4439
       __loop_clr_fd+0x1c0/0x978 drivers/block/loop.c:1384
       lo_release+0x16c/0x204 drivers/block/loop.c:2084
       blkdev_put+0x480/0x6ac block/bdev.c:-1
       blkdev_close+0x74/0xb0 block/fops.c:478
       __fput+0x1c0/0x7f8 fs/file_table.c:311
       ____fput+0x20/0x30 fs/file_table.c:339
       task_work_run+0x12c/0x1e0 kernel/task_work.c:188
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       do_notify_resume+0x24b4/0x3128 arch/arm64/kernel/signal.c:949
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
       el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
  (wq_completion)loop5 --> &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)loop5);

 *** DEADLOCK ***

2 locks held by udevd/4026:
 #0: ffff0000c7d24918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xdc/0x6ac block/bdev.c:915
 #1: ffff0000cc100468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xa4/0x978 drivers/block/loop.c:1366

stack backtrace:
CPU: 0 PID: 4026 Comm: udevd Not tainted 5.15.186-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2011
 check_noncircular+0x240/0x2d4 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
 flush_workqueue+0x11c/0x1024 kernel/workqueue.c:2830
 drain_workqueue+0xa4/0x310 kernel/workqueue.c:2995
 destroy_workqueue+0x80/0x9ac kernel/workqueue.c:4439
 __loop_clr_fd+0x1c0/0x978 drivers/block/loop.c:1384
 lo_release+0x16c/0x204 drivers/block/loop.c:2084
 blkdev_put+0x480/0x6ac block/bdev.c:-1
 blkdev_close+0x74/0xb0 block/fops.c:478
 __fput+0x1c0/0x7f8 fs/file_table.c:311
 ____fput+0x20/0x30 fs/file_table.c:339
 task_work_run+0x12c/0x1e0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 do_notify_resume+0x24b4/0x3128 arch/arm64/kernel/signal.c:949
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
 el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584