do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 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 syzkaller #0 Not tainted ------------------------------------------------------ syz.3.2869/13820 is trying to acquire lock: ffff0000d3e5c0a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: __timer_delete_sync+0x78/0x21c kernel/time/timer.c:1555 but task is already holding lock: ffff80001c7e0a30 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff80001c7e0a30 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x18c/0x54c block/blk-cgroup.c:1529 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:351 [inline] blkg_create+0x924/0x11c4 block/blk-cgroup.c:322 blkcg_init_disk+0x20c/0x480 block/blk-cgroup.c:1286 __alloc_disk_node+0x234/0x438 block/genhd.c:1432 __blk_alloc_disk+0x40/0xb8 block/genhd.c:1471 brd_alloc+0x32c/0x6a4 drivers/block/brd.c:424 brd_init+0x120/0x194 drivers/block/brd.c:529 do_one_initcall+0x278/0x9f0 init/main.c:1270 do_initcall_level+0x158/0x214 init/main.c:1343 do_initcalls+0x58/0xac init/main.c:1359 do_basic_setup+0x8c/0xa0 init/main.c:1378 kernel_init_freeable+0x35c/0x4f0 init/main.c:1598 kernel_init+0x24/0x1d8 init/main.c:1486 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850 -> #1 (&q->queue_lock){..-.}-{2:2}: __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] _raw_spin_lock_irq+0x70/0x98 kernel/locking/spinlock.c:170 spin_lock_irq include/linux/spinlock.h:376 [inline] throtl_pending_timer_fn+0x100/0xe20 block/blk-throttle.c:1200 call_timer_fn+0x1b8/0x96c kernel/time/timer.c:1701 expire_timers kernel/time/timer.c:1752 [inline] __run_timers+0x478/0x6d8 kernel/time/timer.c:2023 run_timer_softirq+0x7c/0x114 kernel/time/timer.c:2036 handle_softirqs+0x318/0xc90 kernel/softirq.c:596 __do_softirq+0x14/0x20 kernel/softirq.c:630 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:80 call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:897 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:85 invoke_softirq kernel/softirq.c:477 [inline] __irq_exit_rcu+0x23c/0x430 kernel/softirq.c:679 irq_exit_rcu+0x14/0x84 kernel/softirq.c:691 __el1_irq arch/arm64/kernel/entry-common.c:472 [inline] el1_interrupt+0x38/0x54 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_enable arch/arm64/include/asm/irqflags.h:35 [inline] raw_spin_rq_unlock_irq kernel/sched/sched.h:1374 [inline] finish_lock_switch+0xb8/0x1c8 kernel/sched/core.c:5005 finish_task_switch+0x120/0x658 kernel/sched/core.c:5123 context_switch kernel/sched/core.c:5249 [inline] __schedule+0xdb8/0x1a6c kernel/sched/core.c:6563 schedule+0xc4/0x170 kernel/sched/core.c:6639 schedule_timeout+0xc8/0x2f4 kernel/time/timer.c:2144 unix_wait_for_peer+0x188/0x264 net/unix/af_unix.c:1449 unix_dgram_sendmsg+0xc84/0x13e4 net/unix/af_unix.c:2051 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] ____sys_sendmsg+0x588/0x90c net/socket.c:2519 ___sys_sendmsg net/socket.c:2573 [inline] __sys_sendmmsg+0x320/0x7ec net/socket.c:2659 __do_sys_sendmmsg net/socket.c:2688 [inline] __se_sys_sendmmsg net/socket.c:2685 [inline] __arm64_sys_sendmmsg+0xa4/0xc0 net/socket.c:2685 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 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:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678 __timer_delete_sync+0xa0/0x21c kernel/time/timer.c:1556 timer_delete_sync+0x24/0x34 kernel/time/timer.c:1629 del_timer_sync include/linux/timer.h:200 [inline] throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x318/0x54c block/blk-cgroup.c:1533 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2415 blkcg_init_disk+0x3d8/0x480 block/blk-cgroup.c:1310 __alloc_disk_node+0x234/0x438 block/genhd.c:1432 __blk_alloc_disk+0x40/0xb8 block/genhd.c:1471 alloc_dev drivers/md/dm.c:2055 [inline] dm_create+0x514/0xf48 drivers/md/dm.c:2259 dev_create+0xf4/0x25c drivers/md/dm-ioctl.c:875 ctl_ioctl drivers/md/dm-ioctl.c:2055 [inline] dm_ctl_ioctl+0xaac/0xf1c drivers/md/dm-ioctl.c:2077 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+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 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.3.2869/13820: #0: ffff0000cf2ddd70 ( &q->queue_lock ){..-.}-{2:2} , at: spin_lock_irq include/linux/spinlock.h:376 [inline] , at: blkcg_deactivate_policy+0xe4/0x54c block/blk-cgroup.c:1522 #1: ffff80001c7e0a30 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] #1: ffff80001c7e0a30 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x18c/0x54c block/blk-cgroup.c:1529 stack backtrace: CPU: 1 PID: 13820 Comm: syz.3.2869 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 dump_backtrace(regs = 0000000000000000 tsk = 0000000000000000) Call trace: dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678 __timer_delete_sync+0xa0/0x21c kernel/time/timer.c:1556 timer_delete_sync+0x24/0x34 kernel/time/timer.c:1629 del_timer_sync include/linux/timer.h:200 [inline] throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x318/0x54c block/blk-cgroup.c:1533 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2415 blkcg_init_disk+0x3d8/0x480 block/blk-cgroup.c:1310 __alloc_disk_node+0x234/0x438 block/genhd.c:1432 __blk_alloc_disk+0x40/0xb8 block/genhd.c:1471 alloc_dev drivers/md/dm.c:2055 [inline] dm_create+0x514/0xf48 drivers/md/dm.c:2259 dev_create+0xf4/0x25c drivers/md/dm-ioctl.c:875 ctl_ioctl drivers/md/dm-ioctl.c:2055 [inline] dm_ctl_ioctl+0xaac/0xf1c drivers/md/dm-ioctl.c:2077 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+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 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 kcov: kcov_task_exit: t = ffff0000d2eb3800, kcov->t = ffff0000d2eb3800