====================================================== WARNING: possible circular locking dependency detected 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0 Not tainted ------------------------------------------------------ syz-executor.3/31589 is trying to acquire lock: ffff0001107d60a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x70/0x1ac kernel/time/timer.c:1417 but task is already holding lock: ffff80000ef84d98 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] ffff80000ef84d98 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0xdc/0x198 block/blk-cgroup.c:1519 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:349 [inline] blkg_create+0x3d0/0x668 block/blk-cgroup.c:344 blkcg_init_queue+0x7c/0x1d8 block/blk-cgroup.c:1285 __alloc_disk_node+0x16c/0x29c block/genhd.c:1367 __blk_alloc_disk+0x40/0xb4 block/genhd.c:1406 brd_alloc+0x190/0x2c8 drivers/block/brd.c:391 brd_init+0xf0/0x1ac drivers/block/brd.c:477 do_one_initcall+0x118/0x22c init/main.c:1296 do_initcall_level+0xac/0xe4 init/main.c:1369 do_initcalls+0x58/0xa8 init/main.c:1385 do_basic_setup+0x20/0x2c init/main.c:1404 kernel_init_freeable+0xb8/0x148 init/main.c:1623 kernel_init+0x24/0x290 init/main.c:1512 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:374 [inline] throtl_pending_timer_fn+0x94/0x39c block/blk-throttle.c:1152 call_timer_fn+0x90/0x144 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers+0x280/0x374 kernel/time/timer.c:1790 run_timer_softirq+0x34/0x5c kernel/time/timer.c:1803 _stext+0x168/0x37c ____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+0x70/0xbc kernel/softirq.c:452 __irq_exit_rcu+0xf0/0x140 kernel/softirq.c:650 irq_exit_rcu+0x10/0x40 kernel/softirq.c:662 __el1_irq arch/arm64/kernel/entry-common.c:471 [inline] el1_interrupt+0x38/0x68 arch/arm64/kernel/entry-common.c:485 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:490 el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:577 __sanitizer_cov_trace_pc+0x3c/0x8c kernel/kcov.c:196 check_preemption_disabled+0x38/0x104 lib/smp_processor_id.c:16 debug_smp_processor_id+0x20/0x2c lib/smp_processor_id.c:60 rcu_dynticks_curr_cpu_in_eqs include/linux/context_tracking.h:121 [inline] rcu_is_watching+0x24/0x74 kernel/rcu/tree.c:718 rcu_read_lock_held_common kernel/rcu/update.c:108 [inline] rcu_read_lock_sched_held+0x18/0x70 kernel/rcu/update.c:123 trace_lock_release+0x64/0x158 include/trace/events/lock.h:69 lock_release+0x3c/0x2b4 kernel/locking/lockdep.c:5677 rcu_lock_release+0x2c/0x38 include/linux/rcupdate.h:285 rcu_read_unlock include/linux/rcupdate.h:739 [inline] netlink_has_listeners+0x20c/0x260 net/netlink/af_netlink.c:1377 uevent_net_broadcast_untagged+0x68/0x1cc lib/kobject_uevent.c:321 kobject_uevent_net_broadcast+0x14c/0x1f8 lib/kobject_uevent.c:409 kobject_uevent_env+0x428/0x5ec lib/kobject_uevent.c:593 kobject_synth_uevent+0x354/0x6a4 lib/kobject_uevent.c:208 uevent_store+0x34/0x80 drivers/base/core.c:2509 dev_attr_store+0x4c/0x70 drivers/base/core.c:2211 sysfs_kf_write+0xf4/0x11c fs/sysfs/file.c:136 kernfs_fop_write_iter+0x1e4/0x294 fs/kernfs/file.c:354 call_write_iter include/linux/fs.h:2187 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x2dc/0x46c fs/read_write.c:578 ksys_write+0xb4/0x160 fs/read_write.c:631 __do_sys_write fs/read_write.c:643 [inline] __se_sys_write fs/read_write.c:640 [inline] __arm64_sys_write+0x24/0x34 fs/read_write.c:640 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall arch/arm64/kernel/syscall.c:52 [inline] el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581 -> #0 ((&sq->pending_timer)){+.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3829 [inline] __lock_acquire+0x1530/0x30a4 kernel/locking/lockdep.c:5053 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5666 del_timer_sync+0x98/0x1ac kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:500 blkcg_deactivate_policy+0x124/0x198 block/blk-cgroup.c:1523 blk_throtl_exit+0x48/0x80 block/blk-throttle.c:2337 blkcg_init_queue+0x198/0x1d8 block/blk-cgroup.c:1304 __alloc_disk_node+0x16c/0x29c block/genhd.c:1367 __blk_mq_alloc_disk+0xbc/0x12c block/blk-mq.c:3942 loop_add+0x1c8/0x418 drivers/block/loop.c:1983 loop_control_ioctl+0xa0/0x384 drivers/block/loop.c:2155 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0xd0/0x140 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall arch/arm64/kernel/syscall.c:52 [inline] el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581 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 *** 2 locks held by syz-executor.3/31589: #0: ffff0001273d2bf0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline] #0: ffff0001273d2bf0 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x98/0x198 block/blk-cgroup.c:1512 #1: ffff80000ef84d98 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] #1: ffff80000ef84d98 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0xdc/0x198 block/blk-cgroup.c:1519 stack backtrace: CPU: 1 PID: 31589 Comm: syz-executor.3 Not tainted 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022 Call trace: dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156 show_stack+0x2c/0x54 arch/arm64/kernel/stacktrace.c:163 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106 dump_stack+0x1c/0x58 lib/dump_stack.c:113 print_circular_bug+0x2c4/0x2c8 kernel/locking/lockdep.c:2053 check_noncircular+0x14c/0x154 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3829 [inline] __lock_acquire+0x1530/0x30a4 kernel/locking/lockdep.c:5053 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5666 del_timer_sync+0x98/0x1ac kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:500 blkcg_deactivate_policy+0x124/0x198 block/blk-cgroup.c:1523 blk_throtl_exit+0x48/0x80 block/blk-throttle.c:2337 blkcg_init_queue+0x198/0x1d8 block/blk-cgroup.c:1304 __alloc_disk_node+0x16c/0x29c block/genhd.c:1367 __blk_mq_alloc_disk+0xbc/0x12c block/blk-mq.c:3942 loop_add+0x1c8/0x418 drivers/block/loop.c:1983 loop_control_ioctl+0xa0/0x384 drivers/block/loop.c:2155 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0xd0/0x140 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall arch/arm64/kernel/syscall.c:52 [inline] el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581