====================================================== WARNING: possible circular locking dependency detected 6.1.16-syzkaller #0 Not tainted ------------------------------------------------------ kworker/u4:7/4446 is trying to acquire lock: ffff0000cc9f10a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x74/0x210 kernel/time/timer.c:1417 but task is already holding lock: ffff800019965b30 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] ffff800019965b30 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1b8/0x4bc block/blk-cgroup.c:1495 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&blkcg->lock){....}-{2:2}: __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x54/0x6c kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:350 [inline] blkg_create+0x9f4/0x1158 block/blk-cgroup.c:336 blkcg_init_disk+0xe4/0x32c block/blk-cgroup.c:1260 __alloc_disk_node+0x26c/0x484 block/genhd.c:1385 __blk_alloc_disk+0x40/0xbc block/genhd.c:1424 brd_alloc+0x2ac/0x5c8 drivers/block/brd.c:397 brd_init+0x108/0x1c4 drivers/block/brd.c:484 do_one_initcall+0x310/0xda4 init/main.c:1303 do_initcall_level+0x154/0x214 init/main.c:1376 do_initcalls+0x58/0xac init/main.c:1392 do_basic_setup+0x8c/0xa0 init/main.c:1411 kernel_init_freeable+0x3a4/0x528 init/main.c:1631 kernel_init+0x24/0x29c init/main.c:1519 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860 -> #1 (&q->queue_lock){..-.}-{2:2}: __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] _raw_spin_lock_irq+0x70/0x9c kernel/locking/spinlock.c:170 spin_lock_irq include/linux/spinlock.h:375 [inline] throtl_pending_timer_fn+0x104/0xdcc block/blk-throttle.c:1193 call_timer_fn+0x270/0xcf4 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers+0x554/0x718 kernel/time/timer.c:1790 run_timer_softirq+0x7c/0x114 kernel/time/timer.c:1803 __do_softirq+0x37c/0xff4 kernel/softirq.c:571 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:79 call_on_irq_stack+0x2c/0x54 arch/arm64/kernel/entry.S:889 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:84 invoke_softirq kernel/softirq.c:452 [inline] __irq_exit_rcu+0x28c/0x534 kernel/softirq.c:650 irq_exit_rcu+0x14/0x84 kernel/softirq.c:662 __el1_irq arch/arm64/kernel/entry-common.c:472 [inline] el1_interrupt+0x38/0x68 arch/arm64/kernel/entry-common.c:486 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:491 el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:577 arch_local_irq_enable arch/arm64/include/asm/irqflags.h:35 [inline] __local_bh_enable_ip+0x260/0x4d0 kernel/softirq.c:401 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline] _raw_spin_unlock_bh+0x48/0x58 kernel/locking/spinlock.c:210 spin_unlock_bh include/linux/spinlock.h:395 [inline] cfg80211_mlme_unregister_socket+0x274/0x8d4 net/wireless/mlme.c:633 nl80211_netlink_notify+0x2fc/0xb58 net/wireless/nl80211.c:19531 notifier_call_chain kernel/notifier.c:87 [inline] blocking_notifier_call_chain+0xf0/0x198 kernel/notifier.c:382 netlink_release+0xe18/0x16f4 net/netlink/af_netlink.c:792 __sock_release net/socket.c:652 [inline] sock_close+0xb8/0x1fc net/socket.c:1370 __fput+0x30c/0x7bc fs/file_table.c:320 ____fput+0x20/0x30 fs/file_table.c:348 task_work_run+0x240/0x2f0 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x2144/0x3470 arch/arm64/kernel/signal.c:1132 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x9c/0x168 arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581 -> #0 ((&sq->pending_timer)){+.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3098 [inline] check_prevs_add kernel/locking/lockdep.c:3217 [inline] validate_chain kernel/locking/lockdep.c:3832 [inline] __lock_acquire+0x3338/0x764c kernel/locking/lockdep.c:5056 lock_acquire+0x300/0x8e4 kernel/locking/lockdep.c:5669 del_timer_sync+0x9c/0x210 kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x2d8/0x4bc block/blk-cgroup.c:1499 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2406 blkcg_exit_disk+0x4c/0x5c block/blk-cgroup.c:1301 disk_release+0x170/0x2d8 block/genhd.c:1171 device_release+0x8c/0x1ac kobject_cleanup lib/kobject.c:681 [inline] kobject_release lib/kobject.c:712 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x2a8/0x41c lib/kobject.c:729 put_device+0x28/0x40 drivers/base/core.c:3772 put_disk+0x4c/0x64 block/genhd.c:1450 nbd_dev_remove drivers/block/nbd.c:253 [inline] nbd_dev_remove_work+0x50/0xe8 drivers/block/nbd.c:269 process_one_work+0x868/0x16f4 kernel/workqueue.c:2289 worker_thread+0x8e4/0xfec kernel/workqueue.c:2436 kthread+0x24c/0x2d4 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860 other info that might help us debug this: Chain exists of: (&sq->pending_timer) --> &q->queue_lock --> &blkcg->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&blkcg->lock); lock(&q->queue_lock); lock(&blkcg->lock); lock((&sq->pending_timer)); *** DEADLOCK *** 5 locks held by kworker/u4:7/4446: #0: ffff0000cc9e0138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work+0x664/0x16f4 kernel/workqueue.c:2262 #1: ffff80001e2c7c20 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work+0x6a8/0x16f4 kernel/workqueue.c:2264 #2: ffff0000cc9e82e0 (&q->blkcg_mutex){+.+.}-{3:3}, at: blkcg_deactivate_policy+0xfc/0x4bc block/blk-cgroup.c:1487 #3: ffff0000cc9e80d0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:375 [inline] #3: ffff0000cc9e80d0 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x108/0x4bc block/blk-cgroup.c:1488 #4: ffff800019965b30 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] #4: ffff800019965b30 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1b8/0x4bc block/blk-cgroup.c:1495 stack backtrace: CPU: 0 PID: 4446 Comm: kworker/u4:7 Not tainted 6.1.16-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 Workqueue: nbd-del nbd_dev_remove_work Call trace: dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2056 check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3098 [inline] check_prevs_add kernel/locking/lockdep.c:3217 [inline] validate_chain kernel/locking/lockdep.c:3832 [inline] __lock_acquire+0x3338/0x764c kernel/locking/lockdep.c:5056 lock_acquire+0x300/0x8e4 kernel/locking/lockdep.c:5669 del_timer_sync+0x9c/0x210 kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x2d8/0x4bc block/blk-cgroup.c:1499 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2406 blkcg_exit_disk+0x4c/0x5c block/blk-cgroup.c:1301 disk_release+0x170/0x2d8 block/genhd.c:1171 device_release+0x8c/0x1ac kobject_cleanup lib/kobject.c:681 [inline] kobject_release lib/kobject.c:712 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x2a8/0x41c lib/kobject.c:729 put_device+0x28/0x40 drivers/base/core.c:3772 put_disk+0x4c/0x64 block/genhd.c:1450 nbd_dev_remove drivers/block/nbd.c:253 [inline] nbd_dev_remove_work+0x50/0xe8 drivers/block/nbd.c:269 process_one_work+0x868/0x16f4 kernel/workqueue.c:2289 worker_thread+0x8e4/0xfec kernel/workqueue.c:2436 kthread+0x24c/0x2d4 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860