====================================================== WARNING: possible circular locking dependency detected 6.0.0-rc7-syzkaller-00029-g3800a713b607 #0 Not tainted ------------------------------------------------------ syz-executor478/7002 is trying to acquire lock: ffff8880254480a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x33/0x1b0 kernel/time/timer.c:1416 but task is already holding lock: ffffffff91345550 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] ffffffff91345550 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy block/blk-cgroup.c:1519 [inline] ffffffff91345550 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x181/0x470 block/blk-cgroup.c:1501 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+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:349 [inline] blkg_create+0x461/0x1020 block/blk-cgroup.c:344 blkcg_init_queue+0xb2/0x620 block/blk-cgroup.c:1285 __alloc_disk_node+0x29d/0x650 block/genhd.c:1367 __blk_alloc_disk+0x35/0x90 block/genhd.c:1406 brd_alloc.part.0+0x27f/0x7a0 drivers/block/brd.c:391 brd_alloc drivers/block/brd.c:374 [inline] brd_init+0x1b8/0x24b drivers/block/brd.c:477 do_one_initcall+0xfe/0x650 init/main.c:1296 do_initcall_level init/main.c:1369 [inline] do_initcalls init/main.c:1385 [inline] do_basic_setup init/main.c:1404 [inline] kernel_init_freeable+0x6b1/0x73a init/main.c:1623 kernel_init+0x1a/0x1d0 init/main.c:1512 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 -> #1 (&q->queue_lock){..-.}-{2:2}: __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170 spin_lock_irq include/linux/spinlock.h:374 [inline] throtl_pending_timer_fn+0xf7/0x1690 block/blk-throttle.c:1152 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d3/0x9c6 kernel/softirq.c:571 invoke_softirq kernel/softirq.c:445 [inline] __irq_exit_rcu+0x123/0x180 kernel/softirq.c:650 irq_exit_rcu+0x5/0x20 kernel/softirq.c:662 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1106 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649 lock_acquire+0x1ef/0x570 kernel/locking/lockdep.c:5634 rcu_lock_acquire include/linux/rcupdate.h:280 [inline] rcu_read_lock include/linux/rcupdate.h:706 [inline] do_notify_parent_cldstop+0x179/0xa40 kernel/signal.c:2159 ptrace_stop.part.0+0x834/0xa80 kernel/signal.c:2293 ptrace_stop kernel/signal.c:2232 [inline] ptrace_do_notify+0x215/0x2b0 kernel/signal.c:2344 ptrace_notify+0xc4/0x140 kernel/signal.c:2356 ptrace_report_syscall include/linux/ptrace.h:420 [inline] ptrace_report_syscall_entry include/linux/ptrace.h:457 [inline] syscall_trace_enter.constprop.0+0xb0/0x240 kernel/entry/common.c:63 do_syscall_64+0x16/0xb0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #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+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 del_timer_sync+0x5b/0x1b0 kernel/time/timer.c:1417 throtl_pd_free+0x15/0x40 block/blk-throttle.c:500 blkcg_deactivate_policy block/blk-cgroup.c:1523 [inline] blkcg_deactivate_policy+0x26c/0x470 block/blk-cgroup.c:1501 blk_throtl_exit+0x8a/0x1a0 block/blk-throttle.c:2337 blkcg_init_queue+0x19b/0x620 block/blk-cgroup.c:1304 __alloc_disk_node+0x29d/0x650 block/genhd.c:1367 __blk_mq_alloc_disk+0x13b/0x1f0 block/blk-mq.c:3942 loop_add+0x3e2/0xaf0 drivers/block/loop.c:1983 loop_control_ioctl+0x133/0x620 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] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd 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-executor478/7002: #0: ffff88807bc63888 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline] #0: ffff88807bc63888 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy block/blk-cgroup.c:1512 [inline] #0: ffff88807bc63888 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x9b/0x470 block/blk-cgroup.c:1501 #1: ffffffff91345550 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] #1: ffffffff91345550 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy block/blk-cgroup.c:1519 [inline] #1: ffffffff91345550 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x181/0x470 block/blk-cgroup.c:1501 stack backtrace: CPU: 0 PID: 7002 Comm: syz-executor478 Not tainted 6.0.0-rc7-syzkaller-00029-g3800a713b607 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 check_noncircular+0x25f/0x2e0 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+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 del_timer_sync+0x5b/0x1b0 kernel/time/timer.c:1417 throtl_pd_free+0x15/0x40 block/blk-throttle.c:500 blkcg_deactivate_policy block/blk-cgroup.c:1523 [inline] blkcg_deactivate_policy+0x26c/0x470 block/blk-cgroup.c:1501 blk_throtl_exit+0x8a/0x1a0 block/blk-throttle.c:2337 blkcg_init_queue+0x19b/0x620 block/blk-cgroup.c:1304 __alloc_disk_node+0x29d/0x650 block/genhd.c:1367 __blk_mq_alloc_disk+0x13b/0x1f0 block/blk-mq.c:3942 loop_add+0x3e2/0xaf0 drivers/block/loop.c:1983 loop_control_ioctl+0x133/0x620 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] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f91bde18069 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffebac2ccb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f91bde18069 RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003 RBP: 00007ffebac2ccd0 R08: 0000000000000002 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004 R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000