======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.8177/6159 is trying to acquire lock:
ffffffff902469a0 (xps_map_mutex){+.+.}-{4:4}, at: netif_reset_xps_queues net/core/dev.c:2804 [inline]
ffffffff902469a0 (xps_map_mutex){+.+.}-{4:4}, at: netif_reset_xps_queues_gt+0x6f/0xc0 net/core/dev.c:2817

but task is already holding lock:
ffffffff8ebe98f0 (cpu_hotplug_lock){++++}-{0:0}, at: netif_reset_xps_queues net/core/dev.c:2803 [inline]
ffffffff8ebe98f0 (cpu_hotplug_lock){++++}-{0:0}, at: netif_reset_xps_queues_gt+0x61/0xc0 net/core/dev.c:2817

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (cpu_hotplug_lock){++++}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       cpus_read_lock+0x42/0x160 kernel/cpu.c:490
       static_key_disable+0x12/0x20 kernel/jump_label.c:247
       __inet_hash_connect+0x258f/0x25a0 net/ipv4/inet_hashtables.c:1081
       tcp_v4_connect+0xcee/0x1950 net/ipv4/tcp_ipv4.c:306
       __inet_stream_connect+0x258/0xe00 net/ipv4/af_inet.c:684
       inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:755
       connect_socket net/socket.c:2141 [inline]
       __sys_connect_file net/socket.c:2166 [inline]
       __sys_connect+0x316/0x450 net/socket.c:2183
       __do_sys_connect net/socket.c:2189 [inline]
       __se_sys_connect net/socket.c:2186 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2186
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100 net/core/sock.c:3830
       lock_sock include/net/sock.h:1713 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:913
       nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:319
       recv_work+0x1cee/0x1e10 drivers/block/nbd.c:1030
       process_one_work kernel/workqueue.c:3396 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532
       process_one_work kernel/workqueue.c:3396 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #5 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532
       process_one_work kernel/workqueue.c:3396 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #4 (set->srcu){.+.+}-{0:0}:
       srcu_lock_sync include/linux/srcu.h:210 [inline]
       __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1462
       elevator_switch+0x1e8/0x7b0 block/elevator.c:576
       elevator_change+0x2fa/0x480 block/elevator.c:681
       elevator_set_default+0x375/0x440 block/elevator.c:754
       blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:992
       __add_disk+0x6cb/0xe30 block/genhd.c:524
       add_disk_fwnode+0x100/0x3a0 block/genhd.c:593
       add_disk include/linux/blkdev.h:798 [inline]
       nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743
       do_one_initcall+0x250/0x870 init/main.c:1357
       do_initcall_level+0x10a/0x1a0 init/main.c:1419
       do_initcalls+0x59/0xa0 init/main.c:1435
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1670
       kernel_init+0x22/0x1d0 init/main.c:1560
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       elevator_change+0x1af/0x480 block/elevator.c:679
       elevator_set_none+0xb5/0x140 block/elevator.c:769
       blk_mq_elv_switch_none block/blk-mq.c:5102 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5147 [inline]
       blk_mq_update_nr_hw_queues+0x5ef/0x19f0 block/blk-mq.c:5212
       nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1530
       nbd_genl_connect+0x167d/0x1cd0 drivers/block/nbd.c:2310
       genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
       netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
       sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800
       __sock_sendmsg net/socket.c:815 [inline]
       ____sys_sendmsg+0x54e/0x850 net/socket.c:2713
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767
       __sys_sendmsg net/socket.c:2799 [inline]
       __do_sys_sendmsg net/socket.c:2804 [inline]
       __se_sys_sendmsg net/socket.c:2802 [inline]
       __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#53){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690 block/blk-core.c:504
       blk_mq_alloc_queue block/blk-mq.c:4420 [inline]
       __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467
       nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1996
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743
       do_one_initcall+0x250/0x870 init/main.c:1357
       do_initcall_level+0x10a/0x1a0 init/main.c:1419
       do_initcalls+0x59/0xa0 init/main.c:1435
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1670
       kernel_init+0x22/0x1d0 init/main.c:1560
       ret_from_fork+0x514/0xb70 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:4375 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4389
       might_alloc include/linux/sched/mm.h:316 [inline]
       slab_pre_alloc_hook mm/slub.c:4636 [inline]
       slab_alloc_node mm/slub.c:4974 [inline]
       __do_kmalloc_node mm/slub.c:5413 [inline]
       __kmalloc_noprof+0xbc/0x720 mm/slub.c:5439
       _kmalloc_noprof include/linux/slab.h:995 [inline]
       _kzalloc_noprof include/linux/slab.h:1312 [inline]
       __netif_set_xps_queue+0x4d8/0x1e30 net/core/dev.c:2937
       virtnet_set_affinity+0x586/0x6c0 drivers/net/virtio_net.c:4008
       init_vqs+0x1085/0x11c0 drivers/net/virtio_net.c:6574
       virtnet_probe+0x21f1/0x48d0 drivers/net/virtio_net.c:6973
       virtio_dev_probe+0xdf6/0x10c0 drivers/virtio/virtio.c:347
       call_driver_probe drivers/base/dd.c:-1 [inline]
       really_probe+0x254/0xae0 drivers/base/dd.c:706
       __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
       driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
       __driver_attach+0x339/0x600 drivers/base/dd.c:1292
       bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
       bus_add_driver+0x345/0x670 drivers/base/bus.c:763
       driver_register+0x23a/0x320 drivers/base/driver.c:174
       virtio_net_driver_init+0x71/0xa0 drivers/net/virtio_net.c:7298
       do_one_initcall+0x250/0x870 init/main.c:1357
       do_initcall_level+0x10a/0x1a0 init/main.c:1419
       do_initcalls+0x59/0xa0 init/main.c:1435
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1670
       kernel_init+0x22/0x1d0 init/main.c:1560
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (xps_map_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3181 [inline]
       check_prevs_add kernel/locking/lockdep.c:3300 [inline]
       validate_chain kernel/locking/lockdep.c:3924 [inline]
       __lock_acquire+0x15ff/0x2e50 kernel/locking/lockdep.c:5254
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5908
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       netif_reset_xps_queues net/core/dev.c:2804 [inline]
       netif_reset_xps_queues_gt+0x6f/0xc0 net/core/dev.c:2817
       netif_set_real_num_tx_queues+0x84b/0xa30 net/core/dev.c:3268
       veth_set_channels+0x46f/0xad0 drivers/net/veth.c:1351
       ethnl_set_channels+0x8d6/0x970 net/ethtool/channels.c:187
       ethnl_default_set_doit+0xa37/0x1080 net/ethtool/netlink.c:948
       genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
       netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
       sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800
       __sock_sendmsg net/socket.c:815 [inline]
       ____sys_sendmsg+0x54e/0x850 net/socket.c:2713
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767
       __sys_sendmsg net/socket.c:2799 [inline]
       __do_sys_sendmsg net/socket.c:2804 [inline]
       __se_sys_sendmsg net/socket.c:2802 [inline]
       __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  xps_map_mutex --> sk_lock-AF_INET --> cpu_hotplug_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(cpu_hotplug_lock);
                               lock(sk_lock-AF_INET);
                               lock(cpu_hotplug_lock);
  lock(xps_map_mutex);

 *** DEADLOCK ***

locks held by syz.1.8177/6159: 3, last CPU#1:
 #0: ffffffff902c1be8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff90250d40 (rtnl_mutex){+.+.}-{4:4}, at: ethnl_default_set_doit+0x854/0x1080 net/ethtool/netlink.c:935
 #2: ffffffff8ebe98f0 (cpu_hotplug_lock){++++}-{0:0}, at: netif_reset_xps_queues net/core/dev.c:2803 [inline]
 #2: ffffffff8ebe98f0 (cpu_hotplug_lock){++++}-{0:0}, at: netif_reset_xps_queues_gt+0x61/0xc0 net/core/dev.c:2817

stack backtrace:
CPU: 1 UID: 0 PID: 6159 Comm: syz.1.8177 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2059
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2191
 check_prev_add kernel/locking/lockdep.c:3181 [inline]
 check_prevs_add kernel/locking/lockdep.c:3300 [inline]
 validate_chain kernel/locking/lockdep.c:3924 [inline]
 __lock_acquire+0x15ff/0x2e50 kernel/locking/lockdep.c:5254
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5908
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 netif_reset_xps_queues net/core/dev.c:2804 [inline]
 netif_reset_xps_queues_gt+0x6f/0xc0 net/core/dev.c:2817
 netif_set_real_num_tx_queues+0x84b/0xa30 net/core/dev.c:3268
 veth_set_channels+0x46f/0xad0 drivers/net/veth.c:1351
 ethnl_set_channels+0x8d6/0x970 net/ethtool/channels.c:187
 ethnl_default_set_doit+0xa37/0x1080 net/ethtool/netlink.c:948
 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
 genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800
 __sock_sendmsg net/socket.c:815 [inline]
 ____sys_sendmsg+0x54e/0x850 net/socket.c:2713
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767
 __sys_sendmsg net/socket.c:2799 [inline]
 __do_sys_sendmsg net/socket.c:2804 [inline]
 __se_sys_sendmsg net/socket.c:2802 [inline]
 __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5491b9e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5492a71028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f5491e26180 RCX: 00007f5491b9e159
RDX: 0000000000000000 RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007f5491c35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5491e26218 R14: 00007f5491e26180 R15: 00007ffdfeff93c8
 </TASK>