syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.1.1414/10567 is trying to acquire lock:
ffff88803997c410 (&set->update_nr_hwq_lock){++++}-{4:4}, at: add_disk_fwnode+0xe7/0x480 block/genhd.c:596

but task is already holding lock:
ffffffff8e74bdd8 (major_names_lock){+.+.}-{4:4}, at: blk_probe_dev block/genhd.c:881 [inline]
ffffffff8e74bdd8 (major_names_lock){+.+.}-{4:4}, at: blk_request_module+0x35/0x2a0 block/genhd.c:897

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (major_names_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
       blk_probe_dev block/genhd.c:881 [inline]
       blk_request_module+0x35/0x2a0 block/genhd.c:897
       blkdev_get_no_open+0x3f/0xe0 block/bdev.c:833
       bdev_file_open_by_dev+0xa0/0x240 block/bdev.c:1054
       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

-> #6 (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

-> #5 (&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
       seq_read_iter+0x3f8/0xe20 fs/seq_file.c:226
       new_sync_read fs/read_write.c:493 [inline]
       vfs_read+0x58b/0xa80 fs/read_write.c:574
       ksys_read+0x156/0x270 fs/read_write.c:717
       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

-> #4 (&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

-> #3 ((work_completion)(&lo->rootcg_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

-> #2 ((wq_completion)loop1){+.+.}-{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
       fput_close_sync+0x11f/0x240 fs/file_table.c:615
       __do_sys_close fs/open.c:1511 [inline]
       __se_sys_close fs/open.c:1496 [inline]
       __x64_sys_close+0x7e/0x110 fs/open.c:1496
       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 (&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
       __del_gendisk+0x127/0x980 block/genhd.c:710
       del_gendisk+0xe7/0x160 block/genhd.c:823
       loop_remove+0x42/0xc0 drivers/block/loop.c:2136
       loop_control_remove drivers/block/loop.c:2195 [inline]
       loop_control_ioctl+0x4ba/0x5b0 drivers/block/loop.c:2237
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
       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 (&set->update_nr_hwq_lock){++++}-{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
       down_read+0x97/0x200 kernel/locking/rwsem.c:1568
       add_disk_fwnode+0xe7/0x480 block/genhd.c:596
       add_disk include/linux/blkdev.h:794 [inline]
       loop_add+0x86e/0xb50 drivers/block/loop.c:2108
       blk_probe_dev block/genhd.c:884 [inline]
       blk_request_module+0x27d/0x2a0 block/genhd.c:-1
       blkdev_get_no_open+0x3f/0xe0 block/bdev.c:833
       blkdev_open+0x1f5/0x620 block/fops.c:688
       do_dentry_open+0x83d/0x13e0 fs/open.c:947
       vfs_open+0x3b/0x350 fs/open.c:1052
       do_open fs/namei.c:4688 [inline]
       path_openat+0x2eea/0x3960 fs/namei.c:4847
       do_file_open+0x23e/0x4a0 fs/namei.c:4876
       do_sys_openat2+0x115/0x200 fs/open.c:1368
       do_sys_open fs/open.c:1374 [inline]
       __do_sys_creat fs/open.c:1452 [inline]
       __se_sys_creat fs/open.c:1446 [inline]
       __x64_sys_creat+0x8f/0xc0 fs/open.c:1446
       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

other info that might help us debug this:

Chain exists of:
  &set->update_nr_hwq_lock --> system_transition_mutex --> major_names_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(major_names_lock);
                               lock(system_transition_mutex);
                               lock(major_names_lock);
  rlock(&set->update_nr_hwq_lock);

 *** DEADLOCK ***

1 lock held by syz.1.1414/10567:
 #0: ffffffff8e74bdd8 (major_names_lock){+.+.}-{4:4}, at: blk_probe_dev block/genhd.c:881 [inline]
 #0: ffffffff8e74bdd8 (major_names_lock){+.+.}-{4:4}, at: blk_request_module+0x35/0x2a0 block/genhd.c:897

stack backtrace:
CPU: 1 UID: 0 PID: 10567 Comm: syz.1.1414 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
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
 down_read+0x97/0x200 kernel/locking/rwsem.c:1568
 add_disk_fwnode+0xe7/0x480 block/genhd.c:596
 add_disk include/linux/blkdev.h:794 [inline]
 loop_add+0x86e/0xb50 drivers/block/loop.c:2108
 blk_probe_dev block/genhd.c:884 [inline]
 blk_request_module+0x27d/0x2a0 block/genhd.c:-1
 blkdev_get_no_open+0x3f/0xe0 block/bdev.c:833
 blkdev_open+0x1f5/0x620 block/fops.c:688
 do_dentry_open+0x83d/0x13e0 fs/open.c:947
 vfs_open+0x3b/0x350 fs/open.c:1052
 do_open fs/namei.c:4688 [inline]
 path_openat+0x2eea/0x3960 fs/namei.c:4847
 do_file_open+0x23e/0x4a0 fs/namei.c:4876
 do_sys_openat2+0x115/0x200 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_creat fs/open.c:1452 [inline]
 __se_sys_creat fs/open.c:1446 [inline]
 __x64_sys_creat+0x8f/0xc0 fs/open.c:1446
 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
RIP: 0033:0x7f1854aace59
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:00007f1852cc4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007f1854d26180 RCX: 00007f1854aace59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000000c0
RBP: 00007f1854b42d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1854d26218 R14: 00007f1854d26180 R15: 00007fff2f749078
 </TASK>
block device autoloading is deprecated and will be removed.