do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 ====================================================== WARNING: possible circular locking dependency detected 6.1.65-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor383/4225 is trying to acquire lock: ffff0000dd8f70a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x74/0x210 kernel/time/timer.c:1417 but task is already holding lock: ffff800019a62cb0 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] ffff800019a62cb0 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1ac/0x4a8 block/blk-cgroup.c:1476 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:320 blkcg_init_disk+0xd0/0x318 block/blk-cgroup.c:1242 __alloc_disk_node+0x26c/0x484 block/genhd.c:1413 __blk_alloc_disk+0x40/0xbc block/genhd.c:1452 brd_alloc+0x2ac/0x5c8 drivers/block/brd.c:397 brd_init+0x108/0x1c4 drivers/block/brd.c:484 do_one_initcall+0x260/0xacc init/main.c:1296 do_initcall_level+0x154/0x214 init/main.c:1369 do_initcalls+0x58/0xac init/main.c:1385 do_basic_setup+0x8c/0xa0 init/main.c:1404 kernel_init_freeable+0x3a4/0x528 init/main.c:1624 kernel_init+0x24/0x29c init/main.c:1512 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:864 -> #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:1200 call_timer_fn+0x1c0/0xa1c 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+0x314/0xe38 kernel/softirq.c:571 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:79 call_on_irq_stack+0x24/0x4c arch/arm64/kernel/entry.S:893 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:84 invoke_softirq kernel/softirq.c:452 [inline] __irq_exit_rcu+0x264/0x4d4 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:581 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline] lock_acquire+0x2ac/0x7cc kernel/locking/lockdep.c:5665 __might_fault+0xc4/0x124 mm/memory.c:5811 _copy_from_user include/linux/uaccess.h:124 [inline] copy_from_user include/linux/uaccess.h:161 [inline] get_timespec64+0xa0/0x2d0 kernel/time/time.c:787 __do_sys_clock_nanosleep kernel/time/posix-timers.c:1297 [inline] __se_sys_clock_nanosleep kernel/time/posix-timers.c:1285 [inline] __arm64_sys_clock_nanosleep+0x1e4/0x38c kernel/time/posix-timers.c:1285 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #0 ((&sq->pending_timer)){+.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x3338/0x7680 kernel/locking/lockdep.c:5049 lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5662 del_timer_sync+0x9c/0x210 kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x2cc/0x4a8 block/blk-cgroup.c:1480 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2413 blkcg_init_disk+0x2a4/0x318 block/blk-cgroup.c:1266 __alloc_disk_node+0x26c/0x484 block/genhd.c:1413 __blk_mq_alloc_disk+0x114/0x1e4 block/blk-mq.c:4100 loop_add+0x2c4/0x8c8 drivers/block/loop.c:2001 loop_control_ioctl+0xec/0x650 drivers/block/loop.c:2173 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+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 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-executor383/4225: #0: ffff0000d54880d0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:375 [inline] #0: ffff0000d54880d0 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0xf4/0x4a8 block/blk-cgroup.c:1469 #1: ffff800019a62cb0 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] #1: ffff800019a62cb0 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1ac/0x4a8 block/blk-cgroup.c:1476 stack backtrace: CPU: 1 PID: 4225 Comm: syz-executor383 Not tainted 6.1.65-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 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/0x58 lib/dump_stack.c:113 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2048 check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x3338/0x7680 kernel/locking/lockdep.c:5049 lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5662 del_timer_sync+0x9c/0x210 kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x2cc/0x4a8 block/blk-cgroup.c:1480 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2413 blkcg_init_disk+0x2a4/0x318 block/blk-cgroup.c:1266 __alloc_disk_node+0x26c/0x484 block/genhd.c:1413 __blk_mq_alloc_disk+0x114/0x1e4 block/blk-mq.c:4100 loop_add+0x2c4/0x8c8 drivers/block/loop.c:2001 loop_control_ioctl+0xec/0x650 drivers/block/loop.c:2173 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+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585