====================================================== WARNING: possible circular locking dependency detected 6.15.0-syzkaller-01599-gddddf9d64f73 #0 Not tainted ------------------------------------------------------ syz.2.6960/19415 is trying to acquire lock: ffff0000147a2358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x104/0x820 block/genhd.c:706 but task is already holding lock: ffff0000147a1368 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0x108/0x1b0 block/genhd.c:818 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&set->update_nr_hwq_lock){++++}-{4:4}: down_write+0xb0/0x1a4 kernel/locking/rwsem.c:1577 blk_mq_update_nr_hw_queues+0x44/0x8e0 block/blk-mq.c:5041 nbd_start_device+0xf8/0x9d0 drivers/block/nbd.c:1476 nbd_start_device_ioctl drivers/block/nbd.c:1527 [inline] __nbd_ioctl drivers/block/nbd.c:1602 [inline] nbd_ioctl+0x178/0xa08 drivers/block/nbd.c:1642 compat_blkdev_ioctl+0x1f8/0x860 block/ioctl.c:760 __do_compat_sys_ioctl fs/ioctl.c:1005 [inline] __se_compat_sys_ioctl fs/ioctl.c:948 [inline] __arm64_compat_sys_ioctl+0x1d0/0x238 fs/ioctl.c:948 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc_compat+0x40/0x68 arch/arm64/kernel/syscall.c:157 el0_svc_compat+0x4c/0x17c arch/arm64/kernel/entry-common.c:887 el0t_32_sync_handler+0x98/0x13c arch/arm64/kernel/entry-common.c:897 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:605 -> #1 (&nbd->config_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x144/0x9d8 kernel/locking/mutex.c:746 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:798 refcount_dec_and_mutex_lock+0x44/0xbc lib/refcount.c:118 nbd_config_put+0x28/0x5b0 drivers/block/nbd.c:1423 nbd_release+0x7c/0x128 drivers/block/nbd.c:1735 blkdev_put_whole+0x98/0xf0 block/bdev.c:721 bdev_release+0x2a4/0x510 block/bdev.c:1144 blkdev_release+0x14/0x24 block/fops.c:684 __fput+0x2c8/0x954 fs/file_table.c:465 fput_close_sync+0xdc/0x230 fs/file_table.c:570 __do_sys_close fs/open.c:1589 [inline] __se_sys_close fs/open.c:1574 [inline] __arm64_sys_close+0x6c/0xbc fs/open.c:1574 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc+0x40/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x50/0x180 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x10c/0x138 arch/arm64/kernel/entry-common.c:762 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 -> #0 (&disk->open_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x1638/0x2380 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x310/0x38c kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x144/0x9d8 kernel/locking/mutex.c:746 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:798 __del_gendisk+0x104/0x820 block/genhd.c:706 del_gendisk+0x110/0x1b0 block/genhd.c:819 loop_remove drivers/block/loop.c:2081 [inline] loop_control_remove drivers/block/loop.c:2140 [inline] loop_control_ioctl+0x38c/0x4cc drivers/block/loop.c:2178 __do_compat_sys_ioctl fs/ioctl.c:1005 [inline] __se_compat_sys_ioctl fs/ioctl.c:948 [inline] __arm64_compat_sys_ioctl+0x1d0/0x238 fs/ioctl.c:948 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc_compat+0x40/0x68 arch/arm64/kernel/syscall.c:157 el0_svc_compat+0x4c/0x17c arch/arm64/kernel/entry-common.c:887 el0t_32_sync_handler+0x98/0x13c arch/arm64/kernel/entry-common.c:897 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:605 other info that might help us debug this: Chain exists of: &disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&set->update_nr_hwq_lock); lock(&nbd->config_lock); lock(&set->update_nr_hwq_lock); lock(&disk->open_mutex); *** DEADLOCK *** 1 lock held by syz.2.6960/19415: #0: ffff0000147a1368 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0x108/0x1b0 block/genhd.c:818 stack backtrace: CPU: 1 UID: 0 PID: 19415 Comm: syz.2.6960 Not tainted 6.15.0-syzkaller-01599-gddddf9d64f73 #0 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:466 (C) __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0xa4/0xf4 lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x28c/0x370 kernel/locking/lockdep.c:2046 check_noncircular+0x168/0x17c kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x1638/0x2380 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x310/0x38c kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x144/0x9d8 kernel/locking/mutex.c:746 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:798 __del_gendisk+0x104/0x820 block/genhd.c:706 del_gendisk+0x110/0x1b0 block/genhd.c:819 loop_remove drivers/block/loop.c:2081 [inline] loop_control_remove drivers/block/loop.c:2140 [inline] loop_control_ioctl+0x38c/0x4cc drivers/block/loop.c:2178 __do_compat_sys_ioctl fs/ioctl.c:1005 [inline] __se_compat_sys_ioctl fs/ioctl.c:948 [inline] __arm64_compat_sys_ioctl+0x1d0/0x238 fs/ioctl.c:948 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc_compat+0x40/0x68 arch/arm64/kernel/syscall.c:157 el0_svc_compat+0x4c/0x17c arch/arm64/kernel/entry-common.c:887 el0t_32_sync_handler+0x98/0x13c arch/arm64/kernel/entry-common.c:897 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:605