====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.413/7532 is trying to acquire lock: ffffffff8e5321a8 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4c/0x14c0 mm/percpu.c:1782 but task is already holding lock: ffff888025e29e18 (&q->q_usage_counter(io)#49){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] ffff888025e29e18 (&q->q_usage_counter(io)#49){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues+0x899/0x1200 block/blk-mq.c:5079 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4399 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4446 nbd_dev_add+0x492/0xbb0 drivers/block/nbd.c:1957 nbd_init+0x1a2/0x3c0 drivers/block/nbd.c:2702 do_one_initcall+0x123/0x6e0 init/main.c:1283 do_initcall_level init/main.c:1345 [inline] do_initcalls init/main.c:1361 [inline] do_basic_setup init/main.c:1380 [inline] kernel_init_freeable+0x5c8/0x920 init/main.c:1593 kernel_init+0x1c/0x2b0 init/main.c:1483 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158 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:4269 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4283 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4951 __alloc_frozen_pages_noprof+0x18b/0x2470 mm/page_alloc.c:5172 __alloc_pages_noprof+0xb/0x1b0 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+0x110/0xb00 mm/percpu-vm.c:285 pcpu_alloc_noprof+0x86a/0x14c0 mm/percpu.c:1870 xt_percpu_counter_alloc+0x13e/0x1b0 net/netfilter/x_tables.c:1934 find_check_entry.constprop.0+0xbc/0x9b0 net/ipv4/netfilter/ip_tables.c:526 translate_table+0xc98/0x1720 net/ipv4/netfilter/ip_tables.c:716 ipt_register_table+0x102/0x430 net/ipv4/netfilter/ip_tables.c:1742 iptable_mangle_table_init+0x40/0x60 net/ipv4/netfilter/iptable_mangle.c:92 xt_find_table_lock+0x2e4/0x520 net/netfilter/x_tables.c:1260 xt_request_find_table_lock+0x28/0xf0 net/netfilter/x_tables.c:1285 get_info+0x19c/0x7c0 net/ipv4/netfilter/ip_tables.c:963 do_ipt_get_ctl+0x169/0xaa0 net/ipv4/netfilter/ip_tables.c:1659 nf_getsockopt+0x7c/0xe0 net/netfilter/nf_sockopt.c:116 ip_getsockopt+0x18c/0x1e0 net/ipv4/ip_sockglue.c:1777 tcp_getsockopt+0xa1/0x100 net/ipv4/tcp.c:4810 do_sock_getsockopt+0x34d/0x440 net/socket.c:2421 __sys_getsockopt+0x12f/0x260 net/socket.c:2450 __do_sys_getsockopt net/socket.c:2457 [inline] __se_sys_getsockopt net/socket.c:2454 [inline] __x64_sys_getsockopt+0xbd/0x160 net/socket.c:2454 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 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:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 pcpu_alloc_noprof+0xb4c/0x14c0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x2ff/0x770 lib/sbitmap.c:126 sbitmap_queue_init_node+0x40/0x4a0 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:546 [inline] blk_mq_init_tags+0x17f/0x320 block/blk-mq-tag.c:571 blk_mq_alloc_rq_map block/blk-mq.c:3534 [inline] blk_mq_alloc_map_and_rqs+0x222/0xeb0 block/blk-mq.c:4097 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4119 [inline] __blk_mq_alloc_map_and_rqs+0x128/0x1f0 block/blk-mq.c:4110 blk_mq_realloc_tag_set_tags block/blk-mq.c:4758 [inline] __blk_mq_update_nr_hw_queues+0xcc1/0x1200 block/blk-mq.c:5081 blk_mq_update_nr_hw_queues+0x3b/0x60 block/blk-mq.c:5133 nbd_start_device+0x1b0/0xd70 drivers/block/nbd.c:1492 nbd_genl_connect+0x134b/0x1c60 drivers/block/nbd.c:2242 genl_family_rcv_msg_doit+0x209/0x2f0 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+0x158/0x420 net/netlink/af_netlink.c:2552 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa98/0xc70 net/socket.c:2630 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2684 __sys_sendmsg+0x16d/0x220 net/socket.c:2716 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 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)#49 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#49); lock(fs_reclaim); lock(&q->q_usage_counter(io)#49); lock(pcpu_alloc_mutex); *** DEADLOCK *** 6 locks held by syz.2.413/7532: #0: ffffffff9018af10 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218 #1: ffffffff9018afc8 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff9018afc8 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff9018afc8 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:57 [inline] #1: ffffffff9018afc8 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x577/0x800 net/netlink/genetlink.c:1209 #2: ffff888025e371c8 (&set->update_nr_hwq_lock){++++}-{4:4}, at: blk_mq_update_nr_hw_queues+0x27/0x60 block/blk-mq.c:5131 #3: ffff888025e370d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x31/0x60 block/blk-mq.c:5132 #4: ffff888025e29e18 (&q->q_usage_counter(io)#49){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] #4: ffff888025e29e18 (&q->q_usage_counter(io)#49){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues+0x899/0x1200 block/blk-mq.c:5079 #5: ffff888025e29e50 (&q->q_usage_counter(queue)#33){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] #5: ffff888025e29e50 (&q->q_usage_counter(queue)#33){+.+.}-{0:0}, at: __blk_mq_update_nr_hw_queues+0x899/0x1200 block/blk-mq.c:5079 stack backtrace: CPU: 0 UID: 0 PID: 7532 Comm: syz.2.413 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 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:2043 check_noncircular+0x14c/0x170 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+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 pcpu_alloc_noprof+0xb4c/0x14c0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x2ff/0x770 lib/sbitmap.c:126 sbitmap_queue_init_node+0x40/0x4a0 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:546 [inline] blk_mq_init_tags+0x17f/0x320 block/blk-mq-tag.c:571 blk_mq_alloc_rq_map block/blk-mq.c:3534 [inline] blk_mq_alloc_map_and_rqs+0x222/0xeb0 block/blk-mq.c:4097 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4119 [inline] __blk_mq_alloc_map_and_rqs+0x128/0x1f0 block/blk-mq.c:4110 blk_mq_realloc_tag_set_tags block/blk-mq.c:4758 [inline] __blk_mq_update_nr_hw_queues+0xcc1/0x1200 block/blk-mq.c:5081 blk_mq_update_nr_hw_queues+0x3b/0x60 block/blk-mq.c:5133 nbd_start_device+0x1b0/0xd70 drivers/block/nbd.c:1492 nbd_genl_connect+0x134b/0x1c60 drivers/block/nbd.c:2242 genl_family_rcv_msg_doit+0x209/0x2f0 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+0x158/0x420 net/netlink/af_netlink.c:2552 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa98/0xc70 net/socket.c:2630 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2684 __sys_sendmsg+0x16d/0x220 net/socket.c:2716 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f25e6f8efc9 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:00007f25e7d7f038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f25e71e6180 RCX: 00007f25e6f8efc9 RDX: 0000000020000000 RSI: 0000200000001ac0 RDI: 000000000000000b RBP: 00007f25e7011f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f25e71e6218 R14: 00007f25e71e6180 R15: 00007ffccd7e1818 nbd0: detected capacity change from 0 to 127