do_el0_svc+0x48/0x140 arch/arm64/kernel/syscall.c:197 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584 ====================================================== WARNING: possible circular locking dependency detected 6.1.0-rc8-syzkaller-33330-ga5541c0811a0 #0 Not tainted ------------------------------------------------------ syz-executor.5/6358 is trying to acquire lock: ffff000111ba68a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x70/0x1ac kernel/time/timer.c:1417 but task is already holding lock: ffff80000f022118 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] ffff80000f022118 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0xdc/0x198 block/blk-cgroup.c:1467 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+0x3f8/0x6b0 block/blk-cgroup.c:319 blkcg_init_disk+0x84/0x1e4 block/blk-cgroup.c:1238 __alloc_disk_node+0x16c/0x29c block/genhd.c:1380 __blk_alloc_disk+0x40/0xb4 block/genhd.c:1419 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:1303 do_initcall_level+0xac/0xe4 init/main.c:1376 do_initcalls+0x58/0xa8 init/main.c:1392 do_basic_setup+0x20/0x2c init/main.c:1411 kernel_init_freeable+0xb8/0x148 init/main.c:1631 kernel_init+0x24/0x290 init/main.c:1519 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:863 -> #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+0xa8/0x80c block/blk-throttle.c:1193 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:80 call_on_irq_stack+0x2c/0x54 arch/arm64/kernel/entry.S:892 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:85 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: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:580 lock_is_held include/linux/lockdep.h:283 [inline] rcu_read_lock_sched_held+0x2c/0x70 kernel/rcu/update.c:125 trace_lock_acquire+0x6c/0x17c include/trace/events/lock.h:24 lock_acquire+0x50/0x1f8 kernel/locking/lockdep.c:5639 rcu_lock_acquire+0x44/0x54 include/linux/rcupdate.h:304 rcu_read_lock include/linux/rcupdate.h:738 [inline] sk_filter_trim_cap+0x12c/0x3f0 net/core/filter.c:145 sk_filter include/linux/filter.h:870 [inline] unix_dgram_sendmsg+0x550/0xb34 net/unix/af_unix.c:1977 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_sendmmsg+0x228/0x56c net/socket.c:2622 __do_sys_sendmmsg net/socket.c:2651 [inline] __se_sys_sendmmsg net/socket.c:2648 [inline] __arm64_sys_sendmmsg+0x30/0x44 net/socket.c:2648 __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+0x48/0x140 arch/arm64/kernel/syscall.c:197 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584 -> #0 ((&sq->pending_timer)){+.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3097 [inline] check_prevs_add kernel/locking/lockdep.c:3216 [inline] validate_chain kernel/locking/lockdep.c:3831 [inline] __lock_acquire+0x1530/0x3084 kernel/locking/lockdep.c:5055 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668 del_timer_sync+0x98/0x1ac kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x124/0x198 block/blk-cgroup.c:1471 blk_throtl_exit+0x4c/0x84 block/blk-throttle.c:2406 blkcg_init_disk+0x1a0/0x1e4 block/blk-cgroup.c:1262 __alloc_disk_node+0x16c/0x29c block/genhd.c:1380 __blk_mq_alloc_disk+0xbc/0x12c block/blk-mq.c:4035 loop_add+0x1c8/0x418 drivers/block/loop.c:1983 loop_control_ioctl+0xa0/0x384 drivers/block/loop.c:2155 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+0x48/0x140 arch/arm64/kernel/syscall.c:197 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584 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.5/6358: #0: ffff000112bf8f40 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:375 [inline] #0: ffff000112bf8f40 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x98/0x198 block/blk-cgroup.c:1460 #1: ffff80000f022118 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] #1: ffff80000f022118 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0xdc/0x198 block/blk-cgroup.c:1467 stack backtrace: CPU: 1 PID: 6358 Comm: syz-executor.5 Not tainted 6.1.0-rc8-syzkaller-33330-ga5541c0811a0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call trace: dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156 show_stack+0x2c/0x3c 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:2055 check_noncircular+0x14c/0x154 kernel/locking/lockdep.c:2177 check_prev_add kernel/locking/lockdep.c:3097 [inline] check_prevs_add kernel/locking/lockdep.c:3216 [inline] validate_chain kernel/locking/lockdep.c:3831 [inline] __lock_acquire+0x1530/0x3084 kernel/locking/lockdep.c:5055 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668 del_timer_sync+0x98/0x1ac kernel/time/timer.c:1417 throtl_pd_free+0x20/0x48 block/blk-throttle.c:493 blkcg_deactivate_policy+0x124/0x198 block/blk-cgroup.c:1471 blk_throtl_exit+0x4c/0x84 block/blk-throttle.c:2406 blkcg_init_disk+0x1a0/0x1e4 block/blk-cgroup.c:1262 __alloc_disk_node+0x16c/0x29c block/genhd.c:1380 __blk_mq_alloc_disk+0xbc/0x12c block/blk-mq.c:4035 loop_add+0x1c8/0x418 drivers/block/loop.c:1983 loop_control_ioctl+0xa0/0x384 drivers/block/loop.c:2155 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+0x48/0x140 arch/arm64/kernel/syscall.c:197 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584