======================================================
WARNING: possible circular locking dependency detected
5.18.0-syzkaller-03023-g7e062cda7d90 #0 Not tainted
------------------------------------------------------
syz-executor.1/2460 is trying to acquire lock:
ffff88801c2d00d0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
ffff88801c2d00d0 (&q->queue_lock){..-.}-{2:2}, at: throtl_pending_timer_fn+0xf7/0x1690 block/blk-throttle.c:1152

but task is already holding lock:
ffffc90004d5fcb8 ((&sq->pending_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:35 [inline]
ffffc90004d5fcb8 ((&sq->pending_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x6b0 kernel/time/timer.c:1464

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 ((&sq->pending_timer)){+.-.}-{0:0}:
       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:1519 [inline]
       blkcg_deactivate_policy+0x2d2/0x4e0 block/blk-cgroup.c:1497
       blk_throtl_exit+0x8a/0x1a0 block/blk-throttle.c:2336
       blkcg_init_queue+0x19b/0x610 block/blk-cgroup.c:1301
       __alloc_disk_node+0x260/0x610 block/genhd.c:1381
       __blk_mq_alloc_disk+0x133/0x1c0 block/blk-mq.c:3941
       nbd_dev_add+0x3b2/0xc90 drivers/block/nbd.c:1764
       nbd_genl_connect+0x11f3/0x1930 drivers/block/nbd.c:1946
       genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731
       genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
       genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:792
       netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2501
       genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
       netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
       netlink_unicast+0x543/0x7f0 net/netlink/af_netlink.c:1345
       netlink_sendmsg+0x917/0xe10 net/netlink/af_netlink.c:1921
       sock_sendmsg_nosec net/socket.c:714 [inline]
       sock_sendmsg+0xcf/0x120 net/socket.c:734
       ____sys_sendmsg+0x6eb/0x810 net/socket.c:2492
       ___sys_sendmsg+0xf3/0x170 net/socket.c:2546
       __sys_sendmsg net/socket.c:2575 [inline]
       __do_sys_sendmsg net/socket.c:2584 [inline]
       __se_sys_sendmsg net/socket.c:2582 [inline]
       __x64_sys_sendmsg+0x132/0x220 net/socket.c:2582
       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+0x46/0xb0

-> #1 (&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+0x45e/0x1000 block/blk-cgroup.c:344
       blkcg_init_queue+0xb2/0x610 block/blk-cgroup.c:1282
       __alloc_disk_node+0x260/0x610 block/genhd.c:1381
       __blk_alloc_disk+0x35/0x70 block/genhd.c:1421
       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+0x103/0x650 init/main.c:1295
       do_initcall_level init/main.c:1368 [inline]
       do_initcalls init/main.c:1384 [inline]
       do_basic_setup init/main.c:1403 [inline]
       kernel_init_freeable+0x6b1/0x73a init/main.c:1610
       kernel_init+0x1a/0x1d0 init/main.c:1499
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302

-> #0 (&q->queue_lock){..-.}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3064 [inline]
       check_prevs_add kernel/locking/lockdep.c:3183 [inline]
       validate_chain kernel/locking/lockdep.c:3798 [inline]
       __lock_acquire+0x2ac6/0x56c0 kernel/locking/lockdep.c:5022
       lock_acquire kernel/locking/lockdep.c:5634 [inline]
       lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5599
       __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+0x1a5/0x6b0 kernel/time/timer.c:1474
       expire_timers kernel/time/timer.c:1519 [inline]
       __run_timers.part.0+0x679/0xa80 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+0x29b/0x9c2 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+0x45/0xc0 arch/x86/kernel/apic/apic.c:1106
       asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:649

other info that might help us debug this:

Chain exists of:
  &q->queue_lock --> &blkcg->lock --> (&sq->pending_timer)

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((&sq->pending_timer));
                               lock(&blkcg->lock);
                               lock((&sq->pending_timer));
  lock(&q->queue_lock);

 *** DEADLOCK ***

1 lock held by syz-executor.1/2460:
 #0: ffffc90004d5fcb8 ((&sq->pending_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:35 [inline]
 #0: ffffc90004d5fcb8 ((&sq->pending_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x6b0 kernel/time/timer.c:1464

stack backtrace:
CPU: 1 PID: 2460 Comm: syz-executor.1 Not tainted 5.18.0-syzkaller-03023-g7e062cda7d90 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __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:2144
 check_prev_add kernel/locking/lockdep.c:3064 [inline]
 check_prevs_add kernel/locking/lockdep.c:3183 [inline]
 validate_chain kernel/locking/lockdep.c:3798 [inline]
 __lock_acquire+0x2ac6/0x56c0 kernel/locking/lockdep.c:5022
 lock_acquire kernel/locking/lockdep.c:5634 [inline]
 lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5599
 __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+0x1a5/0x6b0 kernel/time/timer.c:1474
 expire_timers kernel/time/timer.c:1519 [inline]
 __run_timers.part.0+0x679/0xa80 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+0x29b/0x9c2 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+0x45/0xc0 arch/x86/kernel/apic/apic.c:1106
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:649
RIP: 0033:0x7f6ce8a89109
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:00007f6ce9b1b168 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 00007f6ce8b9bf60 RCX: 00007f6ce8a89109
RDX: 0000000020000040 RSI: 0000000000008933 RDI: 0000000000000004
RBP: 00007f6ce8ae308d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffca0a0492f R14: 00007f6ce9b1b300 R15: 0000000000022000
 </TASK>