====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.284/7315 is trying to acquire lock: ffff80008f843d88 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x224/0x1930 mm/percpu.c:1782 but task is already holding lock: ffff0000cac5c520 (&q->q_usage_counter(io)#34){++++}-{0:0}, at: nbd_start_device+0x158/0xa48 drivers/block/nbd.c:1492 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:4399 [inline] __blk_mq_alloc_disk+0x124/0x304 block/blk-mq.c:4446 nbd_dev_add+0x398/0x820 drivers/block/nbd.c:1957 nbd_init+0x1b4/0x1f4 drivers/block/nbd.c:2702 do_one_initcall+0x250/0x990 init/main.c:1283 do_initcall_level+0x128/0x1c4 init/main.c:1345 do_initcalls+0x70/0xd0 init/main.c:1361 do_basic_setup+0x78/0x8c init/main.c:1380 kernel_init_freeable+0x268/0x39c init/main.c:1593 kernel_init+0x24/0x1dc init/main.c:1483 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4269 [inline] fs_reclaim_acquire+0x8c/0x118 mm/page_alloc.c:4283 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x13c/0x50c mm/page_alloc.c:4951 __alloc_frozen_pages_noprof+0x134/0x318 mm/page_alloc.c:5172 __alloc_pages_noprof+0x18/0x100 mm/page_alloc.c:5217 __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+0xb2c/0x1930 mm/percpu.c:1870 xt_percpu_counter_alloc+0x14c/0x1ec net/netfilter/x_tables.c:1934 find_check_entry net/ipv4/netfilter/ip_tables.c:526 [inline] translate_table+0xe18/0x1824 net/ipv4/netfilter/ip_tables.c:716 ipt_register_table+0xe8/0x5c0 net/ipv4/netfilter/ip_tables.c:1742 iptable_nat_table_init+0x50/0x2ec net/ipv4/netfilter/iptable_nat.c:115 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/ipv4/netfilter/ip_tables.c:963 [inline] do_ipt_get_ctl+0x588/0x1008 net/ipv4/netfilter/ip_tables.c:1659 nf_getsockopt+0x264/0x284 net/netfilter/nf_sockopt.c:116 ip_getsockopt+0x1bc/0x328 net/ipv4/ip_sockglue.c:1777 tcp_getsockopt+0xcc/0xe8 net/ipv4/tcp.c:4810 sock_common_getsockopt+0xa8/0xc4 net/core/sock.c:3885 do_sock_getsockopt+0x248/0x3c4 net/socket.c:2421 __sys_getsockopt net/socket.c:2450 [inline] __do_sys_getsockopt net/socket.c:2457 [inline] __se_sys_getsockopt net/socket.c:2454 [inline] __arm64_sys_getsockopt+0x168/0x1d8 net/socket.c:2454 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x254 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+0x5c/0x254 arch/arm64/kernel/entry-common.c:746 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:765 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #0 (pcpu_alloc_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598 __mutex_lock kernel/locking/mutex.c:760 [inline] _mutex_lock_killable+0x2c/0x38 kernel/locking/mutex.c:828 pcpu_alloc_noprof+0x224/0x1930 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x1c4/0x57c lib/sbitmap.c:126 sbitmap_queue_init_node+0x54/0x484 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:546 [inline] blk_mq_init_tags+0x134/0x278 block/blk-mq-tag.c:571 blk_mq_alloc_rq_map block/blk-mq.c:3534 [inline] blk_mq_alloc_map_and_rqs+0xc8/0xc58 block/blk-mq.c:4097 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4119 [inline] blk_mq_realloc_tag_set_tags block/blk-mq.c:4758 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5081 [inline] blk_mq_update_nr_hw_queues+0x88c/0x1604 block/blk-mq.c:5133 nbd_start_device+0x158/0xa48 drivers/block/nbd.c:1492 nbd_genl_connect+0xf88/0x158c drivers/block/nbd.c:2242 genl_family_rcv_msg_doit+0x1d8/0x2bc net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x450/0x624 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x220/0x3fc net/netlink/af_netlink.c:2552 genl_rcv+0x38/0x50 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x694/0x8c4 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x648/0x930 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0x490/0x7b8 net/socket.c:2630 ___sys_sendmsg+0x204/0x278 net/socket.c:2684 __sys_sendmsg net/socket.c:2716 [inline] __do_sys_sendmsg net/socket.c:2721 [inline] __se_sys_sendmsg net/socket.c:2719 [inline] __arm64_sys_sendmsg+0x184/0x238 net/socket.c:2719 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x254 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+0x5c/0x254 arch/arm64/kernel/entry-common.c:746 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:765 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 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 *** 6 locks held by syz.2.284/7315: #0: ffff8000928bc450 (cb_lock){++++}-{4:4}, at: genl_rcv+0x28/0x50 net/netlink/genetlink.c:1218 #1: ffff8000928bc268 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffff8000928bc268 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffff8000928bc268 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0xf4/0x624 net/netlink/genetlink.c:1209 #2: ffff0000cad571c8 (&set->update_nr_hwq_lock){++++}-{4:4}, at: blk_mq_update_nr_hw_queues+0x98/0x1604 block/blk-mq.c:5131 #3: ffff0000cad570d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0xa4/0x1604 block/blk-mq.c:5132 #4: ffff0000cac5c520 (&q->q_usage_counter(io)#34){++++}-{0:0}, at: nbd_start_device+0x158/0xa48 drivers/block/nbd.c:1492 #5: ffff0000cac5c558 (&q->q_usage_counter(queue)#18){+.+.}-{0:0}, at: nbd_start_device+0x158/0xa48 drivers/block/nbd.c:1492 stack backtrace: CPU: 1 UID: 0 PID: 7315 Comm: syz.2.284 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (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:2043 check_noncircular+0x154/0x174 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598 __mutex_lock kernel/locking/mutex.c:760 [inline] _mutex_lock_killable+0x2c/0x38 kernel/locking/mutex.c:828 pcpu_alloc_noprof+0x224/0x1930 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x1c4/0x57c lib/sbitmap.c:126 sbitmap_queue_init_node+0x54/0x484 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:546 [inline] blk_mq_init_tags+0x134/0x278 block/blk-mq-tag.c:571 blk_mq_alloc_rq_map block/blk-mq.c:3534 [inline] blk_mq_alloc_map_and_rqs+0xc8/0xc58 block/blk-mq.c:4097 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4119 [inline] blk_mq_realloc_tag_set_tags block/blk-mq.c:4758 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5081 [inline] blk_mq_update_nr_hw_queues+0x88c/0x1604 block/blk-mq.c:5133 nbd_start_device+0x158/0xa48 drivers/block/nbd.c:1492 nbd_genl_connect+0xf88/0x158c drivers/block/nbd.c:2242 genl_family_rcv_msg_doit+0x1d8/0x2bc net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x450/0x624 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x220/0x3fc net/netlink/af_netlink.c:2552 genl_rcv+0x38/0x50 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x694/0x8c4 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x648/0x930 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0x490/0x7b8 net/socket.c:2630 ___sys_sendmsg+0x204/0x278 net/socket.c:2684 __sys_sendmsg net/socket.c:2716 [inline] __do_sys_sendmsg net/socket.c:2721 [inline] __se_sys_sendmsg net/socket.c:2719 [inline] __arm64_sys_sendmsg+0x184/0x238 net/socket.c:2719 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x254 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+0x5c/0x254 arch/arm64/kernel/entry-common.c:746 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:765 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 nbd1: detected capacity change from 0 to 127