====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc5-syzkaller-00136-g4d64321c4f6f #0 Not tainted ------------------------------------------------------ syz.0.1150/9917 is trying to acquire lock: ffff888143be85d8 (&q->elevator_lock){+.+.}-{4:4}, at: blk_mq_elv_switch_none block/blk-mq.c:4951 [inline] ffff888143be85d8 (&q->elevator_lock){+.+.}-{4:4}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:5031 [inline] ffff888143be85d8 (&q->elevator_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x49a/0x1a10 block/blk-mq.c:5083 but task is already holding lock: ffff888143be80a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#50){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4348 [inline] __blk_mq_alloc_disk+0x164/0x350 block/blk-mq.c:4395 nbd_dev_add+0x478/0xb10 drivers/block/nbd.c:1933 nbd_init+0x21a/0x2d0 drivers/block/nbd.c:2670 do_one_initcall+0x233/0x820 init/main.c:1257 do_initcall_level+0x137/0x1f0 init/main.c:1319 do_initcalls+0x69/0xd0 init/main.c:1335 kernel_init_freeable+0x3d9/0x570 init/main.c:1567 kernel_init+0x1d/0x1d0 init/main.c:1457 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 __fs_reclaim_acquire mm/page_alloc.c:4064 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4078 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4098 [inline] slab_alloc_node mm/slub.c:4176 [inline] kmem_cache_alloc_noprof+0x44/0x3c0 mm/slub.c:4203 __kernfs_new_node+0xd7/0x7f0 fs/kernfs/dir.c:637 kernfs_new_node+0x102/0x210 fs/kernfs/dir.c:713 kernfs_create_dir_ns+0x44/0x130 fs/kernfs/dir.c:1081 sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x59f/0xb40 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_add+0x155/0x220 lib/kobject.c:426 elv_register_queue+0xdb/0x260 block/elevator.c:462 blk_register_queue+0x375/0x450 block/blk-sysfs.c:874 add_disk_fwnode+0x77f/0x10e0 block/genhd.c:505 add_disk include/linux/blkdev.h:757 [inline] nbd_dev_add+0x710/0xb10 drivers/block/nbd.c:1963 nbd_init+0x21a/0x2d0 drivers/block/nbd.c:2670 do_one_initcall+0x233/0x820 init/main.c:1257 do_initcall_level+0x137/0x1f0 init/main.c:1319 do_initcalls+0x69/0xd0 init/main.c:1335 kernel_init_freeable+0x3d9/0x570 init/main.c:1567 kernel_init+0x1d/0x1d0 init/main.c:1457 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&q->elevator_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 blk_mq_elv_switch_none block/blk-mq.c:4951 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5031 [inline] blk_mq_update_nr_hw_queues+0x49a/0x1a10 block/blk-mq.c:5083 nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2201 genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x758/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x219/0x270 net/socket.c:727 ____sys_sendmsg+0x505/0x830 net/socket.c:2566 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &q->elevator_lock --> fs_reclaim --> &q->q_usage_counter(io)#50 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#50); lock(fs_reclaim); lock(&q->q_usage_counter(io)#50); lock(&q->elevator_lock); *** DEADLOCK *** 6 locks held by syz.0.1150/9917: #0: ffffffff8f358db0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218 #1: ffffffff8f358bc8 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff8f358bc8 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff8f358bc8 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10d/0x790 net/netlink/genetlink.c:1209 #2: ffff88814376a998 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_genl_connect+0x94f/0x1930 drivers/block/nbd.c:2111 #3: ffff88814376a8d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0xac/0x1a10 block/blk-mq.c:5082 #4: ffff888143be80a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 #5: ffff888143be80e0 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 stack backtrace: CPU: 0 UID: 0 PID: 9917 Comm: syz.0.1150 Not tainted 6.15.0-rc5-syzkaller-00136-g4d64321c4f6f #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211 check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 blk_mq_elv_switch_none block/blk-mq.c:4951 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5031 [inline] blk_mq_update_nr_hw_queues+0x49a/0x1a10 block/blk-mq.c:5083 nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2201 genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x758/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x219/0x270 net/socket.c:727 ____sys_sendmsg+0x505/0x830 net/socket.c:2566 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3a8538e969 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3a861f0038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f3a855b6080 RCX: 00007f3a8538e969 RDX: 0000000000000000 RSI: 0000200000001ac0 RDI: 0000000000000007 RBP: 00007f3a85410ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f3a855b6080 R15: 00007ffc21235bb8