====================================================== WARNING: possible circular locking dependency detected 6.15.0-syzkaller-07774-g90b83efa6701 #0 Not tainted ------------------------------------------------------ syz.5.2578/15211 is trying to acquire lock: ffffffff8e2238e8 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x284/0x16b0 mm/percpu.c:1782 but task is already holding lock: ffff888142bb6278 (&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:5871 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4396 [inline] __blk_mq_alloc_disk+0x162/0x340 block/blk-mq.c:4443 nbd_dev_add+0x476/0xb00 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+0x3fc/0x770 arch/x86/kernel/process.c:148 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:5871 __fs_reclaim_acquire mm/page_alloc.c:4056 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4070 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x153/0x610 mm/page_alloc.c:4738 __alloc_frozen_pages_noprof+0x123/0x370 mm/page_alloc.c:4959 __alloc_pages_noprof+0xa/0x30 mm/page_alloc.c:5004 __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+0x182/0xb30 mm/percpu-vm.c:285 pcpu_alloc_noprof+0xcbd/0x16b0 mm/percpu.c:1870 xt_percpu_counter_alloc+0x161/0x220 net/netfilter/x_tables.c:1931 find_check_entry net/ipv4/netfilter/ip_tables.c:526 [inline] translate_table+0x12e9/0x2000 net/ipv4/netfilter/ip_tables.c:716 ipt_register_table+0x106/0x7c0 net/ipv4/netfilter/ip_tables.c:1742 iptable_raw_table_init+0x54/0x80 net/ipv4/netfilter/iptable_raw.c:49 xt_find_table_lock+0x30c/0x3e0 net/netfilter/x_tables.c:1260 xt_request_find_table_lock+0x26/0x100 net/netfilter/x_tables.c:1285 get_info net/ipv4/netfilter/ip_tables.c:963 [inline] do_ipt_get_ctl+0x730/0x1180 net/ipv4/netfilter/ip_tables.c:1659 nf_getsockopt+0x26b/0x290 net/netfilter/nf_sockopt.c:116 ip_getsockopt+0x1c4/0x220 net/ipv4/ip_sockglue.c:1777 do_sock_getsockopt+0x35d/0x650 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] __x64_sys_getsockopt+0x1a5/0x250 net/socket.c:2390 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #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+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 pcpu_alloc_noprof+0x284/0x16b0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x1e1/0x630 lib/sbitmap.c:126 sbitmap_queue_init_node+0x41/0x660 lib/sbitmap.c:438 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x110/0x280 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3538 [inline] blk_mq_alloc_map_and_rqs+0xbd/0x9f0 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+0x76a/0x14c0 block/blk-mq.c:5043 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+0x205/0x470 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+0xfa/0x3b0 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: pcpu_alloc_mutex --> 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(pcpu_alloc_mutex); *** DEADLOCK *** 7 locks held by syz.5.2578/15211: #0: ffffffff8f570970 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218 #1: ffffffff8f570788 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff8f570788 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff8f570788 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10d/0x790 net/netlink/genetlink.c:1209 #2: ffff88802549d230 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_genl_connect+0x94f/0x1930 drivers/block/nbd.c:2111 #3: ffff88802549d188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: blk_mq_update_nr_hw_queues+0x3b/0x14c0 block/blk-mq.c:5041 #4: ffff88802549d0d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x49/0x14c0 block/blk-mq.c:5042 #5: ffff888142bb6278 (&q->q_usage_counter(io)#50){++++}-{0:0}, at: nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 #6: ffff888142bb62b0 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 stack backtrace: CPU: 1 UID: 0 PID: 15211 Comm: syz.5.2578 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #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:2046 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 pcpu_alloc_noprof+0x284/0x16b0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x1e1/0x630 lib/sbitmap.c:126 sbitmap_queue_init_node+0x41/0x660 lib/sbitmap.c:438 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x110/0x280 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3538 [inline] blk_mq_alloc_map_and_rqs+0xbd/0x9f0 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+0x76a/0x14c0 block/blk-mq.c:5043 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+0x205/0x470 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+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f68a998e929 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:00007f68aa8ae038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f68a9bb5fa0 RCX: 00007f68a998e929 RDX: 0000000000004000 RSI: 00002000000027c0 RDI: 000000000000000d RBP: 00007f68a9a10b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f68a9bb5fa0 R15: 00007ffe72fdaaa8 nbd1: detected capacity change from 0 to 32