====================================================== WARNING: possible circular locking dependency detected 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0 Not tainted ------------------------------------------------------ syz-executor.5/26044 is trying to acquire lock: ffff0000f70c98a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x70/0x1ac kernel/time/timer.c:1417 but task is already holding lock: ffff80000eff4298 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] ffff80000eff4298 (&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/0x288 block/genhd.c:1366 __blk_alloc_disk+0x40/0xa4 block/genhd.c:1405 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+0xb8/0x138 init/main.c:1623 kernel_init+0x24/0x290 init/main.c:1512 ret_from_fork+0x10/0x20 -> #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+0x94/0x3d0 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_own_stack include/asm-generic/softirq_stack.h:10 [inline] 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:459 [inline] el1_interrupt+0x38/0x68 arch/arm64/kernel/entry-common.c:473 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:478 el1h_64_irq+0x64/0x68 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline] refill_obj_stock+0x134/0x254 mm/memcontrol.c:3285 obj_cgroup_uncharge+0x14/0x20 mm/memcontrol.c:3339 memcg_slab_free_hook+0x118/0x188 mm/slab.h:564 slab_free mm/slub.c:3529 [inline] kmem_cache_free+0xd8/0x388 mm/slub.c:3551 put_files_struct+0x198/0x1c8 fs/file.c:452 exit_files+0x48/0x64 fs/file.c:464 do_exit+0x220/0xbb8 kernel/exit.c:790 do_group_exit+0x70/0xe8 kernel/exit.c:925 get_signal+0xb0c/0xb30 kernel/signal.c:2857 do_signal+0x128/0x424 arch/arm64/kernel/signal.c:1071 do_notify_resume+0xc0/0x1d0 arch/arm64/kernel/signal.c:1124 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/0x150 arch/arm64/kernel/entry-common.c:625 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642 el0t_64_sync+0x18c/0x190 -> #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/0x288 block/genhd.c:1366 __blk_mq_alloc_disk+0xbc/0x11c block/blk-mq.c:3941 loop_add+0x1c8/0x408 drivers/block/loop.c:1978 loop_control_ioctl+0xa0/0x384 drivers/block/loop.c:2150 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+0x48/0x154 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:624 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642 el0t_64_sync+0x18c/0x190 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.5/26044: #0: ffff0000c4aa3320 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline] #0: ffff0000c4aa3320 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x98/0x198 block/blk-cgroup.c:1512 #1: ffff80000eff4298 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] #1: ffff80000eff4298 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0xdc/0x198 block/blk-cgroup.c:1519 stack backtrace: CPU: 0 PID: 26044 Comm: syz-executor.5 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 Call trace: dump_backtrace+0x1b0/0x1dc arch/arm64/kernel/stacktrace.c:182 show_stack+0x2c/0x64 arch/arm64/kernel/stacktrace.c:189 __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/0x288 block/genhd.c:1366 __blk_mq_alloc_disk+0xbc/0x11c block/blk-mq.c:3941 loop_add+0x1c8/0x408 drivers/block/loop.c:1978 loop_control_ioctl+0xa0/0x384 drivers/block/loop.c:2150 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+0x48/0x154 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:624 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642 el0t_64_sync+0x18c/0x190