syzbot
possible deadlock in blk_request_module
Status:
upstream: reported on 2026/10/20 20:24
Reported-by: syzbot+49e5efd97029dc10b94d@syzkaller.appspotmail.com
First crash: 8d05h, last: 1d17h
Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.8.1436/9582 is trying to acquire lock:
ffffffff8e19d748 (major_names_lock){+.+.}-{3:3}, at: blk_probe_dev block/genhd.c:753 [inline]
ffffffff8e19d748 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x31/0x290 block/genhd.c:769
but task is already holding lock:
ffff888028da82d0 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: mddev_lock drivers/md/md.h:577 [inline]
ffff888028da82d0 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: new_dev_store+0x222/0x660 drivers/md/md.c:4640
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+0x12d/0xae0 kernel/locking/mutex.c:747
mddev_lock drivers/md/md.h:577 [inline]
array_state_store+0x2e4/0x9c0 drivers/md/md.c:4479
md_attr_store+0x183/0x220 drivers/md/md.c:5633
kernfs_fop_write_iter+0x3a0/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2271 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x482/0x9a0 fs/read_write.c:584
ksys_write+0x14d/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
-> #3 (kn->active#73){++++}-{0:0}:
kernfs_drain+0x31a/0x6d0 fs/kernfs/dir.c:499
__kernfs_remove+0x3f4/0x6c0 fs/kernfs/dir.c:1461
kernfs_remove_by_name_ns+0xd8/0x150 fs/kernfs/dir.c:1667
kernfs_remove_by_name include/linux/kernfs.h:622 [inline]
remove_files fs/sysfs/group.c:28 [inline]
sysfs_remove_group+0xfd/0x290 fs/sysfs/group.c:288
sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:312
__kobject_del+0x83/0x2e0 lib/kobject.c:587
kobject_cleanup lib/kobject.c:672 [inline]
kobject_release lib/kobject.c:712 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x22f/0x450 lib/kobject.c:729
process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
-> #2 ((work_completion)(&mddev->del_work)#2){+.+.}-{0:0}:
process_one_work+0x7ec/0x1160 kernel/workqueue.c:2268
worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
-> #1 ((wq_completion)md_misc){+.+.}-{0:0}:
__flush_workqueue+0x165/0x1380 kernel/workqueue.c:2812
md_alloc+0x2e/0xd00 drivers/md/md.c:5708
md_alloc_and_put drivers/md/md.c:5800 [inline]
md_probe+0x53/0xc0 drivers/md/md.c:5813
blk_probe_dev block/genhd.c:756 [inline]
blk_request_module+0x26e/0x290 block/genhd.c:-1
blkdev_get_no_open+0x33/0xc0 block/bdev.c:758
blkdev_get_by_dev+0x77/0xa60 block/bdev.c:815
blkdev_open+0x119/0x2d0 block/fops.c:500
do_dentry_open+0x7dd/0x10b0 fs/open.c:882
do_open fs/namei.c:3677 [inline]
path_openat+0x2674/0x2f10 fs/namei.c:3834
do_filp_open+0x1ee/0x420 fs/namei.c:3861
do_sys_openat2+0x14b/0x4f0 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1347
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 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+0x3a03/0x7ea0 kernel/locking/lockdep.c:5171
lock_acquire+0x1bc/0x4a0 kernel/locking/lockdep.c:5790
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
blk_probe_dev block/genhd.c:753 [inline]
blk_request_module+0x31/0x290 block/genhd.c:769
blkdev_get_no_open+0x33/0xc0 block/bdev.c:758
blkdev_get_by_dev+0x77/0xa60 block/bdev.c:815
lock_rdev drivers/md/md.c:2561 [inline]
md_import_device+0x379/0x800 drivers/md/md.c:3751
new_dev_store+0x38d/0x660 drivers/md/md.c:-1
md_attr_store+0x183/0x220 drivers/md/md.c:5633
kernfs_fop_write_iter+0x3a0/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2271 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x482/0x9a0 fs/read_write.c:584
ksys_write+0x14d/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 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#73 --> &mddev->reconfig_mutex
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mddev->reconfig_mutex);
lock(kn->active#73);
lock(&mddev->reconfig_mutex);
lock(major_names_lock);
*** DEADLOCK ***
5 locks held by syz.8.1436/9582:
#0: ffff8880251305e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2ae/0x360 fs/file.c:1038
#1: ffff88807f688460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x270/0x9a0 fs/read_write.c:580
#2: ffff88801b680088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1d8/0x520 fs/kernfs/file.c:343
#3: ffff8880392b3bd0 (kn->active#71){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
#3: ffff8880392b3bd0 (kn->active#71){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x232/0x520 fs/kernfs/file.c:344
#4: ffff888028da82d0 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: mddev_lock drivers/md/md.h:577 [inline]
#4: ffff888028da82d0 (&mddev->reconfig_mutex){+.+.}-{3:3}, at: new_dev_store+0x222/0x660 drivers/md/md.c:4640
stack backtrace:
CPU: 0 PID: 9582 Comm: syz.8.1436 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
check_noncircular+0x2f8/0x400 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+0x3a03/0x7ea0 kernel/locking/lockdep.c:5171
lock_acquire+0x1bc/0x4a0 kernel/locking/lockdep.c:5790
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
blk_probe_dev block/genhd.c:753 [inline]
blk_request_module+0x31/0x290 block/genhd.c:769
blkdev_get_no_open+0x33/0xc0 block/bdev.c:758
blkdev_get_by_dev+0x77/0xa60 block/bdev.c:815
lock_rdev drivers/md/md.c:2561 [inline]
md_import_device+0x379/0x800 drivers/md/md.c:3751
new_dev_store+0x38d/0x660 drivers/md/md.c:-1
md_attr_store+0x183/0x220 drivers/md/md.c:5633
kernfs_fop_write_iter+0x3a0/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2271 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x482/0x9a0 fs/read_write.c:584
ksys_write+0x14d/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc295d9f559
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:00007fc296cd7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc296025fa0 RCX: 00007fc295d9f559
RDX: 0000000000000016 RSI: 0000200000000280 RDI: 0000000000000006
RBP: 00007fc295e36b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc296026038 R14: 00007fc296025fa0 R15: 00007ffe0d73c4d8
</TASK>
block device autoloading is deprecated and will be removed.
Struck through repros no longer work on HEAD.