====================================================== WARNING: possible circular locking dependency detected 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0 Not tainted ------------------------------------------------------ syz-executor.2/7019 is trying to acquire lock: ffff0000c48a10a8 ((&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 arch_local_irq_enable arch/arm64/include/asm/irqflags.h:35 [inline] raw_spin_rq_unlock_irq kernel/sched/sched.h:1367 [inline] finish_lock_switch+0x9c/0xe8 kernel/sched/core.c:4942 finish_task_switch+0x98/0x270 kernel/sched/core.c:5060 context_switch kernel/sched/core.c:5185 [inline] __schedule+0x418/0x5a0 kernel/sched/core.c:6494 schedule+0x64/0xa4 kernel/sched/core.c:6570 freezable_schedule include/linux/freezer.h:172 [inline] do_nanosleep+0x90/0x2ec kernel/time/hrtimer.c:2044 hrtimer_nanosleep+0x1cc/0x284 kernel/time/hrtimer.c:2097 common_nsleep+0x70/0x88 kernel/time/posix-timers.c:1236 __do_sys_clock_nanosleep kernel/time/posix-timers.c:1276 [inline] __se_sys_clock_nanosleep kernel/time/posix-timers.c:1254 [inline] __arm64_sys_clock_nanosleep+0x1cc/0x1f0 kernel/time/posix-timers.c:1254 __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 nbd_dev_add+0x1c0/0x3a4 drivers/block/nbd.c:1781 nbd_genl_connect+0x2ec/0xcb8 drivers/block/nbd.c:1964 genl_family_rcv_msg_doit net/netlink/genetlink.c:731 [inline] genl_family_rcv_msg net/netlink/genetlink.c:775 [inline] genl_rcv_msg+0x4bc/0x558 net/netlink/genetlink.c:792 netlink_rcv_skb+0xe4/0x1d0 net/netlink/af_netlink.c:2501 genl_rcv+0x38/0x50 net/netlink/genetlink.c:803 netlink_unicast_kernel+0xfc/0x1dc net/netlink/af_netlink.c:1319 netlink_unicast+0x164/0x248 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x484/0x584 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg net/socket.c:734 [inline] ____sys_sendmsg+0x2f8/0x440 net/socket.c:2482 ___sys_sendmsg net/socket.c:2536 [inline] __sys_sendmsg+0x1ac/0x228 net/socket.c:2565 __do_sys_sendmsg net/socket.c:2574 [inline] __se_sys_sendmsg net/socket.c:2572 [inline] __arm64_sys_sendmsg+0x2c/0x3c net/socket.c:2572 __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 *** 4 locks held by syz-executor.2/7019: #0: ffff80000d803c88 (cb_lock){++++}-{3:3}, at: genl_rcv+0x28/0x50 net/netlink/genetlink.c:802 #1: ffff80000d803b98 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline] #1: ffff80000d803b98 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x80/0x558 net/netlink/genetlink.c:790 #2: ffff0000c582b730 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline] #2: ffff0000c582b730 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x98/0x198 block/blk-cgroup.c:1512 #3: ffff80000ef84d98 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] #3: ffff80000ef84d98 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0xdc/0x198 block/blk-cgroup.c:1519 stack backtrace: CPU: 0 PID: 7019 Comm: syz-executor.2 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 nbd_dev_add+0x1c0/0x3a4 drivers/block/nbd.c:1781 nbd_genl_connect+0x2ec/0xcb8 drivers/block/nbd.c:1964 genl_family_rcv_msg_doit net/netlink/genetlink.c:731 [inline] genl_family_rcv_msg net/netlink/genetlink.c:775 [inline] genl_rcv_msg+0x4bc/0x558 net/netlink/genetlink.c:792 netlink_rcv_skb+0xe4/0x1d0 net/netlink/af_netlink.c:2501 genl_rcv+0x38/0x50 net/netlink/genetlink.c:803 netlink_unicast_kernel+0xfc/0x1dc net/netlink/af_netlink.c:1319 netlink_unicast+0x164/0x248 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x484/0x584 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg net/socket.c:734 [inline] ____sys_sendmsg+0x2f8/0x440 net/socket.c:2482 ___sys_sendmsg net/socket.c:2536 [inline] __sys_sendmsg+0x1ac/0x228 net/socket.c:2565 __do_sys_sendmsg net/socket.c:2574 [inline] __se_sys_sendmsg net/socket.c:2572 [inline] __arm64_sys_sendmsg+0x2c/0x3c net/socket.c:2572 __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 nbd: failed to add new device