====================================================== WARNING: possible circular locking dependency detected 6.1.0-rc5-syzkaller-00103-g81ac25651a62 #0 Not tainted ------------------------------------------------------ syz-executor.2/13756 is trying to acquire lock: ffff88807bc3c0a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0xd0/0x2a0 kernel/time/timer.c:1417 but task is already holding lock: ffffffff921b6830 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] ffffffff921b6830 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1ab/0x540 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}: lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668 __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:350 [inline] blkg_create+0xa1d/0x11b0 block/blk-cgroup.c:319 blkcg_init_disk+0xd8/0x340 block/blk-cgroup.c:1238 __alloc_disk_node+0x2cc/0x590 block/genhd.c:1380 __blk_mq_alloc_disk+0x11b/0x1e0 block/blk-mq.c:4035 floppy_alloc_disk+0x54/0x350 drivers/block/floppy.c:4514 do_floppy_init+0x1b1/0xc54 drivers/block/floppy.c:4595 async_run_entry_fn+0xa6/0x400 kernel/async.c:127 process_one_work+0x877/0xdb0 kernel/workqueue.c:2289 worker_thread+0xb14/0x1330 kernel/workqueue.c:2436 kthread+0x266/0x300 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 -> #1 (&q->queue_lock){..-.}-{2:2}: lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] _raw_spin_lock_irq+0xae/0xf0 kernel/locking/spinlock.c:170 spin_lock_irq include/linux/spinlock.h:375 [inline] throtl_pending_timer_fn+0x100/0x1b40 block/blk-throttle.c:1193 call_timer_fn+0xf5/0x210 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers+0x772/0x980 kernel/time/timer.c:1790 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1803 __do_softirq+0x277/0x738 kernel/softirq.c:571 __irq_exit_rcu+0xcf/0x150 kernel/softirq.c:650 irq_exit_rcu+0x5/0x20 kernel/softirq.c:662 sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1107 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649 mod_objcg_state+0x459/0x670 memcg_slab_post_alloc_hook+0x26b/0x330 mm/slab.h:537 slab_post_alloc_hook mm/slab.h:745 [inline] kmem_cache_alloc_bulk+0x469/0x570 mm/slub.c:3854 __io_alloc_req_refill+0x242/0x48f io_uring/io_uring.c:935 io_alloc_req_refill io_uring/io_uring.h:349 [inline] io_submit_sqes+0xc8e/0x1b90 io_uring/io_uring.c:2272 __do_sys_io_uring_enter io_uring/io_uring.c:3220 [inline] __se_sys_io_uring_enter+0x327/0x22e0 io_uring/io_uring.c:3152 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #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+0x1898/0x6ae0 kernel/locking/lockdep.c:3831 __lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5055 lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668 del_timer_sync+0xec/0x2a0 kernel/time/timer.c:1417 throtl_pd_free+0x15/0x40 block/blk-throttle.c:493 blkcg_deactivate_policy+0x328/0x540 block/blk-cgroup.c:1471 blk_throtl_exit+0xa6/0x140 block/blk-throttle.c:2406 blkcg_init_disk+0x2c2/0x340 block/blk-cgroup.c:1262 __alloc_disk_node+0x2cc/0x590 block/genhd.c:1380 __blk_mq_alloc_disk+0x11b/0x1e0 block/blk-mq.c:4035 loop_add+0x325/0x9b0 drivers/block/loop.c:1983 loop_control_ioctl+0x108/0x770 drivers/block/loop.c:2155 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/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-executor.2/13756: #0: ffff8880217c6ce0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:375 [inline] #0: ffff8880217c6ce0 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0xe3/0x540 block/blk-cgroup.c:1460 #1: ffffffff921b6830 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline] #1: ffffffff921b6830 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x1ab/0x540 block/blk-cgroup.c:1467 stack backtrace: CPU: 1 PID: 13756 Comm: syz-executor.2 Not tainted 6.1.0-rc5-syzkaller-00103-g81ac25651a62 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106 check_noncircular+0x2cc/0x390 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+0x1898/0x6ae0 kernel/locking/lockdep.c:3831 __lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5055 lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668 del_timer_sync+0xec/0x2a0 kernel/time/timer.c:1417 throtl_pd_free+0x15/0x40 block/blk-throttle.c:493 blkcg_deactivate_policy+0x328/0x540 block/blk-cgroup.c:1471 blk_throtl_exit+0xa6/0x140 block/blk-throttle.c:2406 blkcg_init_disk+0x2c2/0x340 block/blk-cgroup.c:1262 __alloc_disk_node+0x2cc/0x590 block/genhd.c:1380 __blk_mq_alloc_disk+0x11b/0x1e0 block/blk-mq.c:4035 loop_add+0x325/0x9b0 drivers/block/loop.c:1983 loop_control_ioctl+0x108/0x770 drivers/block/loop.c:2155 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fe66e08b639 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fe66ee91168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fe66e1abf80 RCX: 00007fe66e08b639 RDX: 0000000001000000 RSI: 0000000000004c80 RDI: 0000000000000003 RBP: 00007fe66ee911d0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 00007fff621334cf R14: 00007fe66ee91300 R15: 0000000000022000