====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc4-syzkaller-00296-ge8ab83e34bdc #0 Not tainted ------------------------------------------------------ syz.3.1054/9530 is trying to acquire lock: ffff888106b67ad8 (&q->elevator_lock){+.+.}-{4:4}, at: blk_mq_elv_switch_none block/blk-mq.c:4951 [inline] ffff888106b67ad8 (&q->elevator_lock){+.+.}-{4:4}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:5031 [inline] ffff888106b67ad8 (&q->elevator_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x4a9/0x1370 block/blk-mq.c:5083 but task is already holding lock: ffff888106b675a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:215 [inline] ffff888106b675a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:5023 [inline] ffff888106b675a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: blk_mq_update_nr_hw_queues+0x263/0x1370 block/blk-mq.c:5083 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}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x179/0x290 block/blk-mq.c:4348 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4395 nbd_dev_add+0x49d/0xbb0 drivers/block/nbd.c:1933 nbd_init+0x181/0x320 drivers/block/nbd.c:2670 do_one_initcall+0x120/0x6e0 init/main.c:1257 do_initcall_level init/main.c:1319 [inline] do_initcalls init/main.c:1335 [inline] do_basic_setup init/main.c:1354 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1567 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4064 [inline] fs_reclaim_acquire+0x102/0x150 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+0x53/0x3b0 mm/slub.c:4203 __kernfs_new_node+0xd2/0x8a0 fs/kernfs/dir.c:637 kernfs_new_node+0x13c/0x1e0 fs/kernfs/dir.c:713 kernfs_create_dir_ns+0x4c/0x1a0 fs/kernfs/dir.c:1081 sysfs_create_dir_ns+0x13a/0x2b0 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x2c4/0x9b0 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_add+0x16e/0x240 lib/kobject.c:426 elv_register_queue+0xd3/0x2a0 block/elevator.c:462 blk_register_queue+0x3c4/0x560 block/blk-sysfs.c:874 add_disk_fwnode+0x911/0x13a0 block/genhd.c:505 add_disk include/linux/blkdev.h:757 [inline] nbd_dev_add+0x78e/0xbb0 drivers/block/nbd.c:1963 nbd_init+0x181/0x320 drivers/block/nbd.c:2670 do_one_initcall+0x120/0x6e0 init/main.c:1257 do_initcall_level init/main.c:1319 [inline] do_initcalls init/main.c:1335 [inline] do_basic_setup init/main.c:1354 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1567 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x45/0x80 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 kernel/locking/lockdep.c:3909 [inline] __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235 lock_acquire kernel/locking/lockdep.c:5866 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x199/0xb90 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+0x4a9/0x1370 block/blk-mq.c:5083 nbd_start_device+0x172/0xcd0 drivers/block/nbd.c:1476 nbd_genl_connect+0x120e/0x1c20 drivers/block/nbd.c:2201 genl_family_rcv_msg_doit+0x206/0x2f0 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x55c/0x800 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x16a/0x440 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+0x53a/0x7f0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg net/socket.c:727 [inline] ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620 __sys_sendmsg+0x16d/0x220 net/socket.c:2652 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 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.3.1054/9530: #0: ffffffff901c6c50 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218 #1: ffffffff901c6d08 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff901c6d08 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff901c6d08 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:57 [inline] #1: ffffffff901c6d08 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x577/0x800 net/netlink/genetlink.c:1209 #2: ffff888026245998 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_genl_connect+0xa1a/0x1c20 drivers/block/nbd.c:2111 #3: ffff8880262458d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x8e/0x1370 block/blk-mq.c:5082 #4: ffff888106b675a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:215 [inline] #4: ffff888106b675a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:5023 [inline] #4: ffff888106b675a8 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: blk_mq_update_nr_hw_queues+0x263/0x1370 block/blk-mq.c:5083 #5: ffff888106b675e0 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:215 [inline] #5: ffff888106b675e0 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:5023 [inline] #5: ffff888106b675e0 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: blk_mq_update_nr_hw_queues+0x263/0x1370 block/blk-mq.c:5083 stack backtrace: CPU: 0 UID: 0 PID: 9530 Comm: syz.3.1054 Not tainted 6.15.0-rc4-syzkaller-00296-ge8ab83e34bdc #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079 check_noncircular+0x14c/0x170 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 kernel/locking/lockdep.c:3909 [inline] __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235 lock_acquire kernel/locking/lockdep.c:5866 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x199/0xb90 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+0x4a9/0x1370 block/blk-mq.c:5083 nbd_start_device+0x172/0xcd0 drivers/block/nbd.c:1476 nbd_genl_connect+0x120e/0x1c20 drivers/block/nbd.c:2201 genl_family_rcv_msg_doit+0x206/0x2f0 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x55c/0x800 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x16a/0x440 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+0x53a/0x7f0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg net/socket.c:727 [inline] ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620 __sys_sendmsg+0x16d/0x220 net/socket.c:2652 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f6c1438e969 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:00007f6c151a1038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f6c145b5fa0 RCX: 00007f6c1438e969 RDX: 0000000000000000 RSI: 0000200000000300 RDI: 0000000000000005 RBP: 00007f6c14410ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f6c145b5fa0 R15: 00007fff1d9e9998