====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ kworker/u8:1/13753 is trying to acquire lock: ffff8880213f1878 (&of->mutex){+.+.}-{4:4}, at: kernfs_seq_start+0x5c/0x420 fs/kernfs/file.c:172 but task is already holding lock: ffff888032aabb80 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xb8/0xe20 fs/seq_file.c:183 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&p->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 seq_read_iter+0xb8/0xe20 fs/seq_file.c:183 lo_rw_aio+0xc80/0xf00 include/linux/percpu-rwsem.h:-1 do_req_filebacked drivers/block/loop.c:435 [inline] loop_handle_cmd drivers/block/loop.c:1941 [inline] loop_process_work+0x92a/0x11b0 drivers/block/loop.c:1976 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #4 ((work_completion)(&worker->work)){+.+.}-{0:0}: process_one_work+0x8d7/0x1630 kernel/workqueue.c:3294 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 ((wq_completion)loop5){+.+.}-{0:0}: touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4033 __flush_workqueue+0x14b/0x14f0 kernel/workqueue.c:4075 drain_workqueue+0xd3/0x390 kernel/workqueue.c:4239 __loop_clr_fd drivers/block/loop.c:1130 [inline] lo_release+0x287/0x8f0 drivers/block/loop.c:1767 bdev_release+0x541/0x660 block/bdev.c:-1 blkdev_release+0x15/0x20 block/fops.c:705 __fput+0x461/0xa70 fs/file_table.c:510 task_work_run+0x1d9/0x270 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:67 [inline] exit_to_user_mode_loop+0xf3/0x4d0 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline] do_syscall_64+0x33e/0x560 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&disk->open_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 bdev_open+0xe0/0xcc0 block/bdev.c:953 bdev_file_open_by_dev+0x1be/0x240 block/bdev.c:1067 swsusp_check+0x56/0x490 kernel/power/swap.c:1571 software_resume+0x51/0x4c0 kernel/power/hibernate.c:1023 resume_store+0x333/0x4f0 kernel/power/hibernate.c:1307 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:688 ksys_write+0x156/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (system_transition_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 lock_system_sleep+0x49/0x70 kernel/power/main.c:71 resume_store+0x2ff/0x4f0 kernel/power/hibernate.c:1300 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:688 ksys_write+0x156/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&of->mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3167 [inline] check_prevs_add kernel/locking/lockdep.c:3286 [inline] validate_chain kernel/locking/lockdep.c:3910 [inline] __lock_acquire+0x15a5/0x2d10 kernel/locking/lockdep.c:5239 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 kernfs_seq_start+0x5c/0x420 fs/kernfs/file.c:172 traverse+0x164/0x580 fs/seq_file.c:107 seq_read_iter+0xd09/0xe20 fs/seq_file.c:196 lo_rw_aio+0xc80/0xf00 include/linux/percpu-rwsem.h:-1 do_req_filebacked drivers/block/loop.c:435 [inline] loop_handle_cmd drivers/block/loop.c:1941 [inline] loop_process_work+0x92a/0x11b0 drivers/block/loop.c:1976 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Chain exists of: &of->mutex --> (work_completion)(&worker->work) --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock((work_completion)(&worker->work)); lock(&p->lock); lock(&of->mutex); *** DEADLOCK *** 3 locks held by kworker/u8:1/13753: #0: ffff88803fc01138 ((wq_completion)loop7){+.+.}-{0:0}, at: process_one_work+0x897/0x1630 kernel/workqueue.c:3293 #1: ffffc90006317c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_one_work+0x8be/0x1630 kernel/workqueue.c:3294 #2: ffff888032aabb80 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xb8/0xe20 fs/seq_file.c:183 stack backtrace: CPU: 0 UID: 0 PID: 13753 Comm: kworker/u8:1 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Workqueue: loop7 loop_workfn Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2045 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2177 check_prev_add kernel/locking/lockdep.c:3167 [inline] check_prevs_add kernel/locking/lockdep.c:3286 [inline] validate_chain kernel/locking/lockdep.c:3910 [inline] __lock_acquire+0x15a5/0x2d10 kernel/locking/lockdep.c:5239 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 kernfs_seq_start+0x5c/0x420 fs/kernfs/file.c:172 traverse+0x164/0x580 fs/seq_file.c:107 seq_read_iter+0xd09/0xe20 fs/seq_file.c:196 lo_rw_aio+0xc80/0xf00 include/linux/percpu-rwsem.h:-1 do_req_filebacked drivers/block/loop.c:435 [inline] loop_handle_cmd drivers/block/loop.c:1941 [inline] loop_process_work+0x92a/0x11b0 drivers/block/loop.c:1976 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245