syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.244/5451 is trying to acquire lock:
ffff88805f95e518 (&disk->open_mutex){+.+.}-{3:3}, at: bd_register_pending_holders+0x33/0x310 block/holder.c:161

but task is already holding lock:
ffffffff8c6fb0e8 (major_names_lock){+.+.}-{3:3}, at: blk_probe_dev block/genhd.c:682 [inline]
ffffffff8c6fb0e8 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x31/0x290 block/genhd.c:698

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (major_names_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       blk_probe_dev block/genhd.c:682 [inline]
       blk_request_module+0x31/0x290 block/genhd.c:698
       blkdev_get_no_open+0x38/0x1d0 block/bdev.c:740
       blkdev_get_by_dev+0x77/0xa60 block/bdev.c:807
       swsusp_check+0x9b/0x2a0 kernel/power/swap.c:1526
       software_resume+0xc6/0x3b0 kernel/power/hibernate.c:982
       resume_store+0xe4/0x130 kernel/power/hibernate.c:1184
       kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x712/0xd00 fs/read_write.c:594
       ksys_write+0x14d/0x250 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #6 (system_transition_mutex/1){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       software_resume+0x7c/0x3b0 kernel/power/hibernate.c:937
       resume_store+0xe4/0x130 kernel/power/hibernate.c:1184
       kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x712/0xd00 fs/read_write.c:594
       ksys_write+0x14d/0x250 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #5 (&of->mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       kernfs_seq_start+0x51/0x3c0 fs/kernfs/file.c:112
       seq_read_iter+0x3c4/0xd50 fs/seq_file.c:225
       call_read_iter include/linux/fs.h:2167 [inline]
       new_sync_read fs/read_write.c:404 [inline]
       vfs_read+0x725/0xcf0 fs/read_write.c:485
       ksys_read+0x14d/0x250 fs/read_write.c:623
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #4 (&p->lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       seq_read_iter+0xad/0xd50 fs/seq_file.c:182
       do_iter_readv_writev+0x497/0x600 fs/read_write.c:-1
       do_iter_read+0x20b/0x7c0 fs/read_write.c:790
       lo_read_simple drivers/block/loop.c:392 [inline]
       do_req_filebacked drivers/block/loop.c:663 [inline]
       loop_handle_cmd drivers/block/loop.c:2235 [inline]
       loop_process_work+0x18dc/0x2480 drivers/block/loop.c:2275
       process_one_work+0x863/0x1000 kernel/workqueue.c:2310
       worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
       kthread+0x436/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

-> #3 ((work_completion)(&worker->work)){+.+.}-{0:0}:
       process_one_work+0x7bf/0x1000 kernel/workqueue.c:2286
       worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
       kthread+0x436/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

-> #2 ((null)){+.+.}-{0:0}:
       flush_workqueue+0x142/0x1380 kernel/workqueue.c:2830
       drain_workqueue+0xcf/0x380 kernel/workqueue.c:2995
       destroy_workqueue+0x7b/0xb20 kernel/workqueue.c:4439
       __loop_clr_fd+0x234/0xb90 drivers/block/loop.c:1384
       blkdev_put_whole block/bdev.c:692 [inline]
       blkdev_put+0x53f/0x7d0 block/bdev.c:957
       blkdev_close+0x76/0xa0 block/fops.c:478
       __fput+0x234/0x930 fs/file_table.c:311
       task_work_run+0x125/0x1a0 kernel/task_work.c:188
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
       exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
       __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
       syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
       do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&lo->lo_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_killable_nested+0x17/0x20 kernel/locking/mutex.c:758
       lo_open+0x6a/0x100 drivers/block/loop.c:2056
       blkdev_get_whole+0x90/0x390 block/bdev.c:669
       blkdev_get_by_dev+0x2d0/0xa60 block/bdev.c:827
       blkdev_open+0x12d/0x2c0 block/fops.c:466
       do_dentry_open+0x7ff/0xf80 fs/open.c:826
       do_open fs/namei.c:3616 [inline]
       path_openat+0x2682/0x2f30 fs/namei.c:3750
       do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
       do_sys_openat2+0x142/0x4a0 fs/open.c:1255
       do_sys_open fs/open.c:1271 [inline]
       __do_sys_openat fs/open.c:1287 [inline]
       __se_sys_openat fs/open.c:1282 [inline]
       __x64_sys_openat+0x135/0x160 fs/open.c:1282
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&disk->open_mutex){+.+.}-{3:3}:
       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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       bd_register_pending_holders+0x33/0x310 block/holder.c:161
       device_add_disk+0x5a7/0xd40 block/genhd.c:486
       add_disk include/linux/genhd.h:200 [inline]
       brd_alloc+0x547/0x760 drivers/block/brd.c:444
       blk_probe_dev block/genhd.c:685 [inline]
       blk_request_module+0x26e/0x290 block/genhd.c:-1
       blkdev_get_no_open+0x38/0x1d0 block/bdev.c:740
       blkdev_get_by_dev+0x77/0xa60 block/bdev.c:807
       swsusp_check+0x9b/0x2a0 kernel/power/swap.c:1526
       software_resume+0xc6/0x3b0 kernel/power/hibernate.c:982
       resume_store+0xe4/0x130 kernel/power/hibernate.c:1184
       kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2173 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x712/0xd00 fs/read_write.c:594
       ksys_write+0x14d/0x250 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  &disk->open_mutex --> system_transition_mutex/1 --> major_names_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(major_names_lock);
                               lock(system_transition_mutex/1);
                               lock(major_names_lock);
  lock(&disk->open_mutex);

 *** DEADLOCK ***

6 locks held by syz.3.244/5451:
 #0: ffff8880794b4ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88802cbd0460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
 #2: ffff88805f955c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #3: ffff88801b7f1830 (kn->active#671){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #4: ffffffff8bfd5448 (system_transition_mutex/1){+.+.}-{3:3}, at: software_resume+0x7c/0x3b0 kernel/power/hibernate.c:937
 #5: ffffffff8c6fb0e8 (major_names_lock){+.+.}-{3:3}, at: blk_probe_dev block/genhd.c:682 [inline]
 #5: ffffffff8c6fb0e8 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x31/0x290 block/genhd.c:698

stack backtrace:
CPU: 0 PID: 5451 Comm: syz.3.244 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 bd_register_pending_holders+0x33/0x310 block/holder.c:161
 device_add_disk+0x5a7/0xd40 block/genhd.c:486
 add_disk include/linux/genhd.h:200 [inline]
 brd_alloc+0x547/0x760 drivers/block/brd.c:444
 blk_probe_dev block/genhd.c:685 [inline]
 blk_request_module+0x26e/0x290 block/genhd.c:-1
 blkdev_get_no_open+0x38/0x1d0 block/bdev.c:740
 blkdev_get_by_dev+0x77/0xa60 block/bdev.c:807
 swsusp_check+0x9b/0x2a0 kernel/power/swap.c:1526
 software_resume+0xc6/0x3b0 kernel/power/hibernate.c:982
 resume_store+0xe4/0x130 kernel/power/hibernate.c:1184
 kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa6c76ad749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa6c5914038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fa6c7903fa0 RCX: 00007fa6c76ad749
RDX: 0000000000000012 RSI: 0000200000000040 RDI: 0000000000000007
RBP: 00007fa6c7731f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa6c7904038 R14: 00007fa6c7903fa0 R15: 00007ffc7e96be88
 </TASK>
block device autoloading is deprecated and will be removed.
PM: Image not found (code -22)
comedi comedi0: no devices specified
loop3: detected capacity change from 0 to 4096
ntfs3: Invalid value for dmask.
process 'syz.3.244' launched '/dev/fd/11' with NULL argv: empty string added