====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc1-syzkaller-g39dfc971e42d #0 Not tainted ------------------------------------------------------ syz.1.598/10115 is trying to acquire lock: ffff80008f8eece8 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x224/0x18c0 mm/percpu.c:1782 but task is already holding lock: ffff0000ca638a68 (&q->q_usage_counter(io)#34){++++}-{0:0}, at: nbd_start_device+0x14c/0x9fc 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)#34){++++}-{0:0}: blk_alloc_queue+0x48c/0x54c block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4396 [inline] __blk_mq_alloc_disk+0x12c/0x310 block/blk-mq.c:4443 nbd_dev_add+0x3a0/0x82c drivers/block/nbd.c:1933 nbd_init+0x1f8/0x224 drivers/block/nbd.c:2670 do_one_initcall+0x250/0x990 init/main.c:1273 do_initcall_level+0x154/0x214 init/main.c:1335 do_initcalls+0x84/0xf4 init/main.c:1351 do_basic_setup+0x8c/0xa0 init/main.c:1370 kernel_init_freeable+0x2dc/0x444 init/main.c:1583 kernel_init+0x24/0x1dc init/main.c:1473 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4045 [inline] fs_reclaim_acquire+0x8c/0x118 mm/page_alloc.c:4059 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x13c/0x50c mm/page_alloc.c:4727 __alloc_frozen_pages_noprof+0x134/0x318 mm/page_alloc.c:4948 __alloc_pages_noprof+0x18/0x100 mm/page_alloc.c:4993 __alloc_pages_node_noprof include/linux/gfp.h:284 [inline] alloc_pages_node_noprof include/linux/gfp.h:311 [inline] pcpu_alloc_pages mm/percpu-vm.c:95 [inline] pcpu_populate_chunk+0x28c/0xa28 mm/percpu-vm.c:285 pcpu_alloc_noprof+0xb40/0x18c0 mm/percpu.c:1870 xt_percpu_counter_alloc+0x14c/0x1ec net/netfilter/x_tables.c:1931 find_check_entry net/ipv6/netfilter/ip6_tables.c:545 [inline] translate_table+0xe54/0x185c net/ipv6/netfilter/ip6_tables.c:733 ip6t_register_table+0xe8/0x5c0 net/ipv6/netfilter/ip6_tables.c:1751 ip6table_security_table_init+0x4c/0x78 net/ipv6/netfilter/ip6table_security.c:45 xt_find_table_lock+0x22c/0x3c8 net/netfilter/x_tables.c:1260 xt_request_find_table_lock+0x38/0x114 net/netfilter/x_tables.c:1285 get_info net/ipv6/netfilter/ip6_tables.c:979 [inline] do_ip6t_get_ctl+0x588/0xff4 net/ipv6/netfilter/ip6_tables.c:1668 nf_getsockopt+0x264/0x284 net/netfilter/nf_sockopt.c:116 ipv6_getsockopt+0x220/0x3a0 net/ipv6/ipv6_sockglue.c:1493 tcp_getsockopt+0xcc/0xe8 net/ipv4/tcp.c:4760 sock_common_getsockopt+0xa8/0xc4 net/core/sock.c:3917 do_sock_getsockopt+0x248/0x3c4 net/socket.c:2357 __sys_getsockopt net/socket.c:2386 [inline] __do_sys_getsockopt net/socket.c:2393 [inline] __se_sys_getsockopt net/socket.c:2390 [inline] __arm64_sys_getsockopt+0x168/0x1d8 net/socket.c:2390 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 -> #0 (pcpu_alloc_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+0x1774/0x30a4 kernel/locking/lockdep.c:5240 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871 __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] _mutex_lock_killable+0x2c/0x38 kernel/locking/mutex.c:815 pcpu_alloc_noprof+0x224/0x18c0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x1c4/0x578 lib/sbitmap.c:126 sbitmap_queue_init_node+0x5c/0x5f8 lib/sbitmap.c:438 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x104/0x248 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3538 [inline] blk_mq_alloc_map_and_rqs+0xc8/0xc30 block/blk-mq.c:4094 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4116 [inline] blk_mq_realloc_tag_set_tags block/blk-mq.c:4755 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:4995 [inline] blk_mq_update_nr_hw_queues+0x590/0x10ec block/blk-mq.c:5043 nbd_start_device+0x14c/0x9fc 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+0x52c/0xc4c drivers/block/nbd.c:1642 blkdev_ioctl+0x610/0xac0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:893 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 other info that might help us debug this: Chain exists of: pcpu_alloc_mutex --> fs_reclaim --> &q->q_usage_counter(io)#34 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#34); lock(fs_reclaim); lock(&q->q_usage_counter(io)#34); lock(pcpu_alloc_mutex); *** DEADLOCK *** 5 locks held by syz.1.598/10115: #0: ffff0000ca636a30 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_ioctl+0x124/0xc4c drivers/block/nbd.c:1635 #1: ffff0000ca636988 (&set->update_nr_hwq_lock){++++}-{4:4}, at: blk_mq_update_nr_hw_queues+0x44/0x10ec block/blk-mq.c:5041 #2: ffff0000ca6368d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x50/0x10ec block/blk-mq.c:5042 #3: ffff0000ca638a68 (&q->q_usage_counter(io)#34){++++}-{0:0}, at: nbd_start_device+0x14c/0x9fc drivers/block/nbd.c:1476 #4: ffff0000ca638aa0 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: nbd_start_device+0x14c/0x9fc drivers/block/nbd.c:1476 stack backtrace: CPU: 0 UID: 0 PID: 10115 Comm: syz.1.598 Not tainted 6.16.0-rc1-syzkaller-g39dfc971e42d #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2046 check_noncircular+0x154/0x174 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+0x1774/0x30a4 kernel/locking/lockdep.c:5240 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871 __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] _mutex_lock_killable+0x2c/0x38 kernel/locking/mutex.c:815 pcpu_alloc_noprof+0x224/0x18c0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x1c4/0x578 lib/sbitmap.c:126 sbitmap_queue_init_node+0x5c/0x5f8 lib/sbitmap.c:438 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x104/0x248 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3538 [inline] blk_mq_alloc_map_and_rqs+0xc8/0xc30 block/blk-mq.c:4094 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4116 [inline] blk_mq_realloc_tag_set_tags block/blk-mq.c:4755 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:4995 [inline] blk_mq_update_nr_hw_queues+0x590/0x10ec block/blk-mq.c:5043 nbd_start_device+0x14c/0x9fc 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+0x52c/0xc4c drivers/block/nbd.c:1642 blkdev_ioctl+0x610/0xac0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:893 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 block nbd1: shutting down sockets