======================================================
WARNING: possible circular locking dependency detected
6.1.16-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/20110 is trying to acquire lock:
ffff888021bed3f0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:375 [inline]
ffff888021bed3f0 (&q->queue_lock){..-.}-{2:2}, at: throtl_pending_timer_fn+0x10d/0x1be0 block/blk-throttle.c:1193

but task is already holding lock:
ffffc900001e0bc0 ((&sq->pending_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:41 [inline]
ffffc900001e0bc0 ((&sq->pending_timer)){+.-.}-{0:0}, at: call_timer_fn+0xbd/0x840 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}:
       lock_acquire+0x23a/0x630 kernel/locking/lockdep.c:5669
       del_timer_sync+0x111/0x2e0 kernel/time/timer.c:1417
       throtl_pd_free+0x15/0x40 block/blk-throttle.c:493
       blkcg_deactivate_policy+0x32d/0x550 block/blk-cgroup.c:1499
       blk_throtl_exit+0xa6/0x140 block/blk-throttle.c:2406
       disk_release+0x1dd/0x380 block/genhd.c:1171
       device_release+0x91/0x1c0
       kobject_cleanup lib/kobject.c:681 [inline]
       kobject_release lib/kobject.c:712 [inline]
       kref_put include/linux/kref.h:65 [inline]
       kobject_put+0x224/0x460 lib/kobject.c:729
       do_floppy_init+0x373/0xc59 drivers/block/floppy.c:4758
       async_run_entry_fn+0xa2/0x410 kernel/async.c:127
       process_one_work+0x909/0x1380 kernel/workqueue.c:2289
       worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
       kthread+0x268/0x300 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #1 (&blkcg->lock){....}-{2:2}:
       lock_acquire+0x23a/0x630 kernel/locking/lockdep.c:5669
       __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+0xa94/0x1280 block/blk-cgroup.c:336
       blkcg_init_disk+0xee/0x350 block/blk-cgroup.c:1260
       __alloc_disk_node+0x2ce/0x590 block/genhd.c:1385
       __blk_alloc_disk+0x2c/0x80 block/genhd.c:1424
       brd_alloc+0x2f9/0x6a0 drivers/block/brd.c:397
       brd_init+0x100/0x1c2 drivers/block/brd.c:484
       do_one_initcall+0x2d6/0xa80 init/main.c:1303
       do_initcall_level+0x157/0x207 init/main.c:1376
       do_initcalls+0x49/0x86 init/main.c:1392
       kernel_init_freeable+0x473/0x61f init/main.c:1631
       kernel_init+0x19/0x290 init/main.c:1519
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #0 (&q->queue_lock){..-.}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3098 [inline]
       check_prevs_add kernel/locking/lockdep.c:3217 [inline]
       validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
       lock_acquire+0x23a/0x630 kernel/locking/lockdep.c:5669
       __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
       _raw_spin_lock_irq+0xcf/0x110 kernel/locking/spinlock.c:170
       spin_lock_irq include/linux/spinlock.h:375 [inline]
       throtl_pending_timer_fn+0x10d/0x1be0 block/blk-throttle.c:1193
       call_timer_fn+0x200/0x840 kernel/time/timer.c:1474
       expire_timers kernel/time/timer.c:1519 [inline]
       __run_timers+0x67c/0x890 kernel/time/timer.c:1790
       run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1803
       __do_softirq+0x30d/0xb1b kernel/softirq.c:571
       invoke_softirq kernel/softirq.c:445 [inline]
       __irq_exit_rcu+0x155/0x240 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
       __sanitizer_cov_trace_pc+0x41/0x60 kernel/kcov.c:212
       signal_pending+0x1b/0xa0 include/linux/sched/signal.h:393
       unix_dgram_sendmsg+0x13a3/0x2050 net/unix/af_unix.c:2050
       sock_sendmsg_nosec net/socket.c:716 [inline]
       sock_sendmsg net/socket.c:736 [inline]
       ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2482
       ___sys_sendmsg net/socket.c:2536 [inline]
       __sys_sendmmsg+0x3ab/0x730 net/socket.c:2622
       __do_sys_sendmmsg net/socket.c:2651 [inline]
       __se_sys_sendmmsg net/socket.c:2648 [inline]
       __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2648
       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:
  &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.0/20110:
 #0: ffffc900001e0bc0 ((&sq->pending_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:41 [inline]
 #0: ffffc900001e0bc0 ((&sq->pending_timer)){+.-.}-{0:0}, at: call_timer_fn+0xbd/0x840 kernel/time/timer.c:1464

stack backtrace:
CPU: 1 PID: 20110 Comm: syz-executor.0 Not tainted 6.1.16-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3098 [inline]
 check_prevs_add kernel/locking/lockdep.c:3217 [inline]
 validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
 lock_acquire+0x23a/0x630 kernel/locking/lockdep.c:5669
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0xcf/0x110 kernel/locking/spinlock.c:170
 spin_lock_irq include/linux/spinlock.h:375 [inline]
 throtl_pending_timer_fn+0x10d/0x1be0 block/blk-throttle.c:1193
 call_timer_fn+0x200/0x840 kernel/time/timer.c:1474
 expire_timers kernel/time/timer.c:1519 [inline]
 __run_timers+0x67c/0x890 kernel/time/timer.c:1790
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1803
 __do_softirq+0x30d/0xb1b kernel/softirq.c:571
 invoke_softirq kernel/softirq.c:445 [inline]
 __irq_exit_rcu+0x155/0x240 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
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649
RIP: 0010:__sanitizer_cov_trace_pc+0x41/0x60 kernel/kcov.c:212
Code: ff 00 74 11 f7 c2 00 01 00 00 74 35 83 b9 8c 15 00 00 00 74 2c 8b 91 68 15 00 00 83 fa 02 75 21 48 8b 91 70 15 00 00 48 8b 32 <48> 8d 7e 01 8b 89 6c 15 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2
RSP: 0018:ffffc9000315f6c8 EFLAGS: 00000246
RAX: ffffffff894528bb RBX: ffff888037cd1d40 RCX: ffff888037cd1d40
RDX: ffffc90005fc9000 RSI: 000000000003ffff RDI: ffff888037cd1d40
RBP: ffffc9000315f8b0 R08: ffffffff894611f0 R09: ffffed1006f9a3a9
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff1100fab6a8c
R13: 000000000000000b R14: dffffc0000000000 R15: ffff88807d5b53ec
 signal_pending+0x1b/0xa0 include/linux/sched/signal.h:393
 unix_dgram_sendmsg+0x13a3/0x2050 net/unix/af_unix.c:2050
 sock_sendmsg_nosec net/socket.c:716 [inline]
 sock_sendmsg net/socket.c:736 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2482
 ___sys_sendmsg net/socket.c:2536 [inline]
 __sys_sendmmsg+0x3ab/0x730 net/socket.c:2622
 __do_sys_sendmmsg net/socket.c:2651 [inline]
 __se_sys_sendmmsg net/socket.c:2648 [inline]
 __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2648
 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: 0033:0x7f5542a8c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f554384e168 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f5542babf80 RCX: 00007f5542a8c0f9
RDX: 0000000000000318 RSI: 00000000200bd000 RDI: 0000000000000005
RBP: 00007f5542ae7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc1f240dcf R14: 00007f554384e300 R15: 0000000000022000
 </TASK>
----------------
Code disassembly (best guess):
   0:	ff 00                	incl   (%rax)
   2:	74 11                	je     0x15
   4:	f7 c2 00 01 00 00    	test   $0x100,%edx
   a:	74 35                	je     0x41
   c:	83 b9 8c 15 00 00 00 	cmpl   $0x0,0x158c(%rcx)
  13:	74 2c                	je     0x41
  15:	8b 91 68 15 00 00    	mov    0x1568(%rcx),%edx
  1b:	83 fa 02             	cmp    $0x2,%edx
  1e:	75 21                	jne    0x41
  20:	48 8b 91 70 15 00 00 	mov    0x1570(%rcx),%rdx
  27:	48 8b 32             	mov    (%rdx),%rsi
* 2a:	48 8d 7e 01          	lea    0x1(%rsi),%rdi <-- trapping instruction
  2e:	8b 89 6c 15 00 00    	mov    0x156c(%rcx),%ecx
  34:	48 39 cf             	cmp    %rcx,%rdi
  37:	73 08                	jae    0x41
  39:	48 89 3a             	mov    %rdi,(%rdx)
  3c:	48                   	rex.W
  3d:	89                   	.byte 0x89
  3e:	44                   	rex.R
  3f:	f2                   	repnz