syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.3.300/6843 is trying to acquire lock:
ffff88802672b4c8 (&disk->open_mutex#4){+.+.}-{4:4}, at: bdev_open+0xe0/0xcc0 block/bdev.c:948

but task is already holding lock:
ffffffff8e075558 (system_transition_mutex){+.+.}-{4:4}, at: software_resume+0x47/0x4c0 kernel/power/hibernate.c:1022

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (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+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&of->mutex){+.+.}-{4:4}:
       __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

-> #3 (&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

-> #2 ((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

-> #1 ((wq_completion)loop9){+.+.}-{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:681
       __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+0x193/0x680 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+0x353/0x580 arch/x86/entry/syscall_64.c:100
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&disk->open_mutex#4){+.+.}-{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
       bdev_open+0xe0/0xcc0 block/bdev.c:948
       bdev_file_open_by_dev+0x1be/0x240 block/bdev.c:1062
       swsusp_check+0x56/0x490 kernel/power/swap.c:1564
       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+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &disk->open_mutex#4 --> &of->mutex --> system_transition_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(system_transition_mutex);
                               lock(&of->mutex);
                               lock(system_transition_mutex);
  lock(&disk->open_mutex#4);

 *** DEADLOCK ***

5 locks held by syz.3.300/6843:
 #0: ffff88803a63b728 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1260
 #1: ffff8880359a2480 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2733 [inline]
 #1: ffff8880359a2480 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:684
 #2: ffff888033bda878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
 #3: ffff88801f2aa008 (kn->active#71){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #3: ffff88801f2aa008 (kn->active#71){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x232/0x540 fs/kernfs/file.c:344
 #4: ffffffff8e075558 (system_transition_mutex){+.+.}-{4:4}, at: software_resume+0x47/0x4c0 kernel/power/hibernate.c:1022

stack backtrace:
CPU: 0 UID: 0 PID: 6843 Comm: syz.3.300 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 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
 bdev_open+0xe0/0xcc0 block/bdev.c:948
 bdev_file_open_by_dev+0x1be/0x240 block/bdev.c:1062
 swsusp_check+0x56/0x490 kernel/power/swap.c:1564
 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+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f601639ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f60145b4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6016616180 RCX: 00007f601639ce59
RDX: 000000000000fdef RSI: 0000200000000040 RDI: 0000000000000005
RBP: 00007f6016432d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6016616218 R14: 00007f6016616180 R15: 00007ffef8b30068
 </TASK>
PM: Image not found (code -5)