syzbot
possible deadlock in netif_reset_xps_queues_gt (3)
Status:
upstream: reported on 2026/07/19 18:17
Subsystems:
kernel
Labels:
prio:normal
[Documentation on labels]
Reported-by: syzbot+95de3405a31a366207c7@syzkaller.appspotmail.com
First crash: 52d, last: 1d03h
Sample crash report:
netdevsim netdevsim3 eth3 (unregistering): unset [0, 1] type 1 family 0 port 256 - 0
netdevsim netdevsim3 eth3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor/17675 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:
-> #7 (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_slow_inc+0x12/0x30 kernel/jump_label.c:190
nbd_genl_reconnect_sock_cb+0x69a/0xbb0 drivers/block/nbd.c:1377
nbd_genl_foreach_sock+0x265/0x450 drivers/block/nbd.c:2152
nbd_genl_reconfigure+0xbbb/0x1040 drivers/block/nbd.c:2477
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
-> #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
unregister_netdevice_many_notify+0x1beb/0x2140 net/core/dev.c:12554
unregister_netdevice_many net/core/dev.c:12589 [inline]
unregister_netdevice_queue+0x2f5/0x340 net/core/dev.c:12390
unregister_netdevice include/linux/netdevice.h:3487 [inline]
nsim_destroy+0x275/0x800 drivers/net/netdevsim/netdev.c:1198
__nsim_dev_port_del+0x14e/0x200 drivers/net/netdevsim/dev.c:1472
nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1486 [inline]
nsim_dev_reload_destroy+0x288/0x490 drivers/net/netdevsim/dev.c:1710
nsim_drv_remove+0x58/0x170 drivers/net/netdevsim/dev.c:1725
device_remove drivers/base/dd.c:616 [inline]
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
bus_remove_device+0x444/0x560 drivers/base/bus.c:664
device_del+0x524/0x8f0 drivers/base/core.c:3965
device_unregister+0x21/0xf0 drivers/base/core.c:4006
nsim_bus_dev_del drivers/net/netdevsim/bus.c:488 [inline]
del_device_store+0x2b5/0x370 drivers/net/netdevsim/bus.c:244
kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
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 --> &nsock->tx_lock --> cpu_hotplug_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(cpu_hotplug_lock);
lock(&nsock->tx_lock);
lock(cpu_hotplug_lock);
lock(xps_map_mutex);
*** DEADLOCK ***
locks held by syz-executor/17675: 8, last CPU#0:
#0: ffff888036fec460 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2753 [inline]
#0: ffff888036fec460 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 fs/read_write.c:683
#1: ffff888029eb5880 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540 fs/kernfs/file.c:336
#2: ffff8880296991e8 (kn->active#51){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline]
#2: ffff8880296991e8 (kn->active#51){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x22b/0x540 fs/kernfs/file.c:337
#3: ffffffff8fac89e0 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd6/0x370 drivers/net/netdevsim/bus.c:234
#4: ffff8880365c7128 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#4: ffff8880365c7128 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1171 [inline]
#4: ffff8880365c7128 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb9/0x880 drivers/base/dd.c:1369
#5: ffff8880365c6258 (&devlink->lock_key#3){+.+.}-{4:4}, at: nsim_drv_remove+0x50/0x170 drivers/net/netdevsim/dev.c:1724
#6: ffffffff90250d40 (rtnl_mutex){+.+.}-{4:4}, at: nsim_destroy+0x173/0x800 drivers/net/netdevsim/netdev.c:1193
#7: ffffffff8ebe98f0 (cpu_hotplug_lock){++++}-{0:0}, at: netif_reset_xps_queues net/core/dev.c:2803 [inline]
#7: ffffffff8ebe98f0 (cpu_hotplug_lock){++++}-{0:0}, at: netif_reset_xps_queues_gt+0x61/0xc0 net/core/dev.c:2817
stack backtrace:
CPU: 0 UID: 0 PID: 17675 Comm: syz-executor 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
unregister_netdevice_many_notify+0x1beb/0x2140 net/core/dev.c:12554
unregister_netdevice_many net/core/dev.c:12589 [inline]
unregister_netdevice_queue+0x2f5/0x340 net/core/dev.c:12390
unregister_netdevice include/linux/netdevice.h:3487 [inline]
nsim_destroy+0x275/0x800 drivers/net/netdevsim/netdev.c:1198
__nsim_dev_port_del+0x14e/0x200 drivers/net/netdevsim/dev.c:1472
nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1486 [inline]
nsim_dev_reload_destroy+0x288/0x490 drivers/net/netdevsim/dev.c:1710
nsim_drv_remove+0x58/0x170 drivers/net/netdevsim/dev.c:1725
device_remove drivers/base/dd.c:616 [inline]
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
bus_remove_device+0x444/0x560 drivers/base/bus.c:664
device_del+0x524/0x8f0 drivers/base/core.c:3965
device_unregister+0x21/0xf0 drivers/base/core.c:4006
nsim_bus_dev_del drivers/net/netdevsim/bus.c:488 [inline]
del_device_store+0x2b5/0x370 drivers/net/netdevsim/bus.c:244
kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
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: 0033:0x7f179eb5e98e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffe069eb058 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055558c11a500 RCX: 00007f179eb5e98e
RDX: 0000000000000001 RSI: 00007ffe069eb0e0 RDI: 0000000000000005
RBP: 00007f179ec358a7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffe069eb0e0 R14: 00007f179f954620 R15: 0000000000000003
</TASK>
netdevsim netdevsim3 eth2 (unregistering): unset [0, 0] type 1 family 0 port 8472 - 0
netdevsim netdevsim3 eth2 (unregistering): unset [0, 1] type 1 family 0 port 256 - 0
netdevsim netdevsim3 eth2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim3 eth1 (unregistering): unset [0, 0] type 1 family 0 port 8472 - 0
netdevsim netdevsim3 eth1 (unregistering): unset [0, 1] type 1 family 0 port 256 - 0
netdevsim netdevsim3 eth1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim3 eth0 (unregistering): unset [0, 0] type 1 family 0 port 8472 - 0
netdevsim netdevsim3 eth0 (unregistering): unset [0, 1] type 1 family 0 port 256 - 0
netdevsim netdevsim3 eth0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
Struck through repros no longer work on HEAD.