syzbot
possible deadlock in blk_request_module
Status:
upstream: reported on 2026/09/05 07:50
Reported-by: syzbot+086639defea9c90fec13@syzkaller.appspotmail.com
First crash: 47d, last: 1d00h
Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.9.3793/19825 is trying to acquire lock:
ffffffff8e5b3688 (major_names_lock){+.+.}-{3:3}, at: blk_probe_dev block/genhd.c:779 [inline]
ffffffff8e5b3688 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x35/0x290 block/genhd.c:795
but task is already holding lock:
ffff888079278360 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: mddev_lock drivers/md/md.h:593 [inline]
ffff888079278360 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: new_dev_store+0x21e/0x650 drivers/md/md.c:4718
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #4 (&mddev->reconfig_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
mddev_lock drivers/md/md.h:593 [inline]
array_state_store+0x2ef/0xb00 drivers/md/md.c:4572
md_attr_store+0x19c/0x390 drivers/md/md.c:5756
kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2019 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x474/0x9a0 fs/read_write.c:584
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #3 (kn->active#79){++++}-{0:0}:
kernfs_drain+0x31e/0x6d0 fs/kernfs/dir.c:500
__kernfs_remove+0x426/0x830 fs/kernfs/dir.c:1486
kernfs_remove_by_name_ns+0xdc/0x150 fs/kernfs/dir.c:1695
kernfs_remove_by_name include/linux/kernfs.h:624 [inline]
remove_files fs/sysfs/group.c:28 [inline]
sysfs_remove_group+0x101/0x290 fs/sysfs/group.c:292
sysfs_remove_groups+0x54/0xa0 fs/sysfs/group.c:316
__kobject_del+0x83/0x2e0 lib/kobject.c:595
kobject_cleanup lib/kobject.c:680 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x233/0x450 lib/kobject.c:737
process_one_work kernel/workqueue.c:2657 [inline]
process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
-> #2 ((work_completion)(&mddev->del_work)){+.+.}-{0:0}:
process_one_work kernel/workqueue.c:2633 [inline]
process_scheduled_works+0x9ab/0x1600 kernel/workqueue.c:2734
worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
-> #1 ((wq_completion)md_misc){+.+.}-{0:0}:
touch_wq_lockdep_map kernel/workqueue.c:3183 [inline]
__flush_workqueue+0x169/0x1380 kernel/workqueue.c:3213
md_alloc+0x33/0xe90 drivers/md/md.c:5831
md_alloc_and_put+0x1a/0x1b0 drivers/md/md.c:5922
blk_probe_dev block/genhd.c:782 [inline]
blk_request_module+0x272/0x290 block/genhd.c:-1
blkdev_get_no_open+0x37/0xc0 block/bdev.c:724
blkdev_get_by_dev+0x64/0x610 block/bdev.c:782
blkdev_open+0x14e/0x360 block/fops.c:589
do_dentry_open+0x880/0x14b0 fs/open.c:929
do_open fs/namei.c:3695 [inline]
path_openat+0x284f/0x3270 fs/namei.c:3856
do_filp_open+0x1f2/0x430 fs/namei.c:3883
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #0 (major_names_lock){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3162 [inline]
check_prevs_add kernel/locking/lockdep.c:3281 [inline]
validate_chain kernel/locking/lockdep.c:3897 [inline]
__lock_acquire+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
blk_probe_dev block/genhd.c:779 [inline]
blk_request_module+0x35/0x290 block/genhd.c:795
blkdev_get_no_open+0x37/0xc0 block/bdev.c:724
blkdev_get_by_dev+0x64/0x610 block/bdev.c:782
md_import_device+0x398/0x7b0 drivers/md/md.c:3838
new_dev_store+0x389/0x650 drivers/md/md.c:-1
md_attr_store+0x19c/0x390 drivers/md/md.c:5756
kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2019 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x474/0x9a0 fs/read_write.c:584
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
other info that might help us debug this:
Chain exists of:
major_names_lock --> kn->active#79 --> &mddev->reconfig_mutex
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mddev->reconfig_mutex);
lock(kn->active#79);
lock(&mddev->reconfig_mutex);
lock(major_names_lock);
*** DEADLOCK ***
5 locks held by syz.9.3793/19825:
#0: ffff88805e010fc8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88802e398418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffff88805ebd4088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x520 fs/kernfs/file.c:343
#3: ffff88807b08b8c0 (kn->active#78){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
#3: ffff88807b08b8c0 (kn->active#78){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x236/0x520 fs/kernfs/file.c:344
#4: ffff888079278360 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: mddev_lock drivers/md/md.h:593 [inline]
#4: ffff888079278360 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: new_dev_store+0x21e/0x650 drivers/md/md.c:4718
stack backtrace:
CPU: 0 PID: 19825 Comm: syz.9.3793 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2215
check_prev_add kernel/locking/lockdep.c:3162 [inline]
check_prevs_add kernel/locking/lockdep.c:3281 [inline]
validate_chain kernel/locking/lockdep.c:3897 [inline]
__lock_acquire+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
blk_probe_dev block/genhd.c:779 [inline]
blk_request_module+0x35/0x290 block/genhd.c:795
blkdev_get_no_open+0x37/0xc0 block/bdev.c:724
blkdev_get_by_dev+0x64/0x610 block/bdev.c:782
md_import_device+0x398/0x7b0 drivers/md/md.c:3838
new_dev_store+0x389/0x650 drivers/md/md.c:-1
md_attr_store+0x19c/0x390 drivers/md/md.c:5756
kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2019 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x474/0x9a0 fs/read_write.c:584
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f015ed9f559
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:00007f015fcaa028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f015f025fa0 RCX: 00007f015ed9f559
RDX: 0000000000000016 RSI: 00002000000002c0 RDI: 0000000000000004
RBP: 00007f015ee36b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f015f026038 R14: 00007f015f025fa0 R15: 00007ffd5599e688
</TASK>
block device autoloading is deprecated and will be removed.
* Struck through repros no longer work on HEAD.