WARNING: possible circular locking dependency detected 6.1.72-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.3/14625 is trying to acquire lock: ffff0000f8bca0a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x74/0x210 kernel/time/timer.c:1417 but task is already holding lock: ffff800019a73cb0 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] ffff800019a73cb0 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1ac/0x4a8 block/blk-cgroup.c:1489 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:1255 __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] ___slab_alloc+0xd18/0xee0 mm/slub.c:3132 __slab_alloc mm/slub.c:3279 [inline] slab_alloc_node mm/slub.c:3364 [inline] __kmem_cache_alloc_node+0x2c8/0x388 mm/slub.c:3437 __do_kmalloc_node mm/slab_common.c:954 [inline] __kmalloc_node_track_caller+0xbc/0x1c0 mm/slab_common.c:975 kmalloc_reserve net/core/skbuff.c:446 [inline] __alloc_skb+0x180/0x580 net/core/skbuff.c:515 alloc_skb include/linux/skbuff.h:1276 [inline] nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline] nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline] nsim_dev_trap_report_work+0x1f0/0x924 drivers/net/netdevsim/dev.c:850 process_one_work+0x7ac/0x1404 kernel/workqueue.c:2292 worker_thread+0x8e4/0xfec kernel/workqueue.c:2439 kthread+0x250/0x2d8 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:864 -> #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:1493 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2415 blkcg_init_disk+0x2a4/0x318 block/blk-cgroup.c:1279 __alloc_disk_node+0x26c/0x484 block/genhd.c:1413 __blk_mq_alloc_disk+0x114/0x1e4 block/blk-mq.c:4101 nbd_dev_add+0x314/0x938 drivers/block/nbd.c:1805 nbd_genl_connect+0x8fc/0x17f4 drivers/block/nbd.c:1988 genl_family_rcv_msg_doit net/netlink/genetlink.c:756 [inline] genl_family_rcv_msg net/netlink/genetlink.c:833 [inline] genl_rcv_msg+0x948/0xc2c net/netlink/genetlink.c:850 netlink_rcv_skb+0x20c/0x3b8 net/netlink/af_netlink.c:2508 genl_rcv+0x38/0x50 net/netlink/genetlink.c:861 netlink_unicast_kernel net/netlink/af_netlink.c:1326 [inline] netlink_unicast+0x65c/0x898 net/netlink/af_netlink.c:1352 netlink_sendmsg+0x834/0xb18 net/netlink/af_netlink.c:1874 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] ____sys_sendmsg+0x55c/0x848 net/socket.c:2514 ___sys_sendmsg net/socket.c:2568 [inline] __sys_sendmsg+0x26c/0x33c net/socket.c:2597 __do_sys_sendmsg net/socket.c:2606 [inline] __se_sys_sendmsg net/socket.c:2604 [inline] __arm64_sys_sendmsg+0x80/0x94 net/socket.c:2604 __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 *** 4 locks held by syz-executor.3/14625: #0: ffff800017e66330 (cb_lock){++++}-{3:3}, at: genl_rcv+0x28/0x50 net/netlink/genetlink.c:860 #1: ffff800017e661e8 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline] #1: ffff800017e661e8 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x114/0xc2c net/netlink/genetlink.c:848 #2: ffff00010c0a80d0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:375 [inline] #2: ffff00010c0a80d0 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0xf4/0x4a8 block/blk-cgroup.c:1482 #3: ffff800019a73cb0 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] #3: ffff800019a73cb0 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1ac/0x4a8 block/blk-cgroup.c:1489 stack backtrace: CPU: 1 PID: 14625 Comm: syz-executor.3 Not tainted 6.1.72-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023 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:1493 blk_throtl_exit+0x9c/0x13c block/blk-throttle.c:2415 blkcg_init_disk+0x2a4/0x318 block/blk-cgroup.c:1279 __alloc_disk_node+0x26c/0x484 block/genhd.c:1413 __blk_mq_alloc_disk+0x114/0x1e4 block/blk-mq.c:4101 nbd_dev_add+0x314/0x938 drivers/block/nbd.c:1805 nbd_genl_connect+0x8fc/0x17f4 drivers/block/nbd.c:1988 genl_family_rcv_msg_doit net/netlink/genetlink.c:756 [inline] genl_family_rcv_msg net/netlink/genetlink.c:833 [inline] genl_rcv_msg+0x948/0xc2c net/netlink/genetlink.c:850 netlink_rcv_skb+0x20c/0x3b8 net/netlink/af_netlink.c:2508 genl_rcv+0x38/0x50 net/netlink/genetlink.c:861 netlink_unicast_kernel net/netlink/af_netlink.c:1326 [inline] netlink_unicast+0x65c/0x898 net/netlink/af_netlink.c:1352 netlink_sendmsg+0x834/0xb18 net/netlink/af_netlink.c:1874 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] ____sys_sendmsg+0x55c/0x848 net/socket.c:2514 ___sys_sendmsg net/socket.c:2568 [inline] __sys_sendmsg+0x26c/0x33c net/socket.c:2597 __do_sys_sendmsg net/socket.c:2606 [inline] __se_sys_sendmsg net/socket.c:2604 [inline] __arm64_sys_sendmsg+0x80/0x94 net/socket.c:2604 __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 nbd: failed to add new device