==================================================================
BUG: KCSAN: data-race in virtqueue_get_buf_ctx / vring_interrupt

write to 0xffff88821ab7f888 of 2 bytes by interrupt on cpu 0:
 virtqueue_get_buf_ctx_split drivers/virtio/virtio_ring.c:721 [inline]
 virtqueue_get_buf_ctx+0x4cc/0x5c0 drivers/virtio/virtio_ring.c:1900
 virtqueue_get_buf+0x29/0x40 drivers/virtio/virtio_ring.c:1906
 free_old_xmit_skbs+0x9e/0x170 drivers/net/virtio_net.c:1359
 start_xmit+0xd3/0xbe0 drivers/net/virtio_net.c:1562
 __netdev_start_xmit include/linux/netdevice.h:4447 [inline]
 netdev_start_xmit include/linux/netdevice.h:4461 [inline]
 xmit_one net/core/dev.c:3420 [inline]
 dev_hard_start_xmit+0xef/0x430 net/core/dev.c:3436
 sch_direct_xmit+0x2b3/0x900 net/sched/sch_generic.c:313
 __dev_xmit_skb net/core/dev.c:3621 [inline]
 __dev_queue_xmit+0x13e2/0x1ba0 net/core/dev.c:3982
 dev_queue_xmit+0x21/0x30 net/core/dev.c:4046
 neigh_hh_output include/net/neighbour.h:500 [inline]
 neigh_output include/net/neighbour.h:509 [inline]
 ip_finish_output2+0x89b/0xea0 net/ipv4/ip_output.c:228
 __ip_finish_output net/ipv4/ip_output.c:308 [inline]
 __ip_finish_output+0x23a/0x490 net/ipv4/ip_output.c:290
 ip_finish_output+0x41/0x160 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:296 [inline]
 ip_output+0xfe/0x230 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:436 [inline]
 ip_local_out+0x74/0x90 net/ipv4/ip_output.c:125
 __ip_queue_xmit+0x3a8/0xa40 net/ipv4/ip_output.c:532
 ip_queue_xmit+0x45/0x60 include/net/ip.h:237
 __tcp_transmit_skb+0xea3/0x1df0 net/ipv4/tcp_output.c:1170
 __tcp_send_ack+0x246/0x300 net/ipv4/tcp_output.c:3697
 tcp_send_ack+0x34/0x40 net/ipv4/tcp_output.c:3703
 __tcp_ack_snd_check+0xd9/0x580 net/ipv4/tcp_input.c:5243
 tcp_rcv_established+0xce9/0xf50 net/ipv4/tcp_input.c:5674
 tcp_v4_do_rcv+0x3b5/0x520 net/ipv4/tcp_ipv4.c:1562
 tcp_v4_rcv+0x1b2a/0x1d20 net/ipv4/tcp_ipv4.c:1943
 ip_protocol_deliver_rcu+0x4d/0x420 net/ipv4/ip_input.c:204
 ip_local_deliver_finish+0x110/0x140 net/ipv4/ip_input.c:231
 NF_HOOK include/linux/netfilter.h:307 [inline]
 NF_HOOK include/linux/netfilter.h:301 [inline]
 ip_local_deliver+0x133/0x210 net/ipv4/ip_input.c:252
 dst_input include/net/dst.h:442 [inline]
 ip_sublist_rcv_finish+0xf8/0x140 net/ipv4/ip_input.c:549
 ip_list_rcv_finish net/ipv4/ip_input.c:599 [inline]
 ip_sublist_rcv+0x418/0x550 net/ipv4/ip_input.c:607
 ip_list_rcv+0x2f5/0x322 net/ipv4/ip_input.c:642
 __netif_receive_skb_list_ptype net/core/dev.c:5193 [inline]
 __netif_receive_skb_list_ptype net/core/dev.c:5182 [inline]
 __netif_receive_skb_list_core+0x350/0x5c0 net/core/dev.c:5241
 __netif_receive_skb_list net/core/dev.c:5293 [inline]
 netif_receive_skb_list_internal+0x5d8/0x830 net/core/dev.c:5388
 gro_normal_list.part.0+0x3a/0xb0 net/core/dev.c:5810
 gro_normal_list net/core/dev.c:6216 [inline]
 napi_complete_done+0x1e4/0x3c0 net/core/dev.c:6203
 virtqueue_napi_complete+0x3a/0xa0 drivers/net/virtio_net.c:329
 virtnet_poll+0x7a6/0x7d0 drivers/net/virtio_net.c:1432
 napi_poll net/core/dev.c:6532 [inline]
 net_rx_action+0x3ae/0xa90 net/core/dev.c:6600
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 do_IRQ+0x81/0x130 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x21
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
 kcsan_setup_watchpoint+0x1d4/0x460 kernel/kcsan/core.c:429
 check_access kernel/kcsan/core.c:459 [inline]
 __tsan_unaligned_write8+0xc7/0x110 kernel/kcsan/core.c:589
 do_nanosleep+0x1da/0x320 kernel/time/hrtimer.c:1881
 hrtimer_nanosleep+0x191/0x320 kernel/time/hrtimer.c:1927
 __do_sys_nanosleep kernel/time/hrtimer.c:1961 [inline]
 __se_sys_nanosleep kernel/time/hrtimer.c:1948 [inline]
 __x64_sys_nanosleep+0x106/0x150 kernel/time/hrtimer.c:1948
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88821ab7f888 of 2 bytes by interrupt on cpu 1:
 more_used drivers/virtio/virtio_ring.c:2029 [inline]
 vring_interrupt+0x36/0x1c0 drivers/virtio/virtio_ring.c:2036
 __handle_irq_event_percpu+0x9a/0x430 kernel/irq/handle.c:149
 handle_irq_event_percpu+0x4b/0xe0 kernel/irq/handle.c:189
 handle_irq_event+0x85/0xca kernel/irq/handle.c:206
 handle_edge_irq+0x1a4/0x4a0 kernel/irq/chip.c:830
 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline]
 do_IRQ+0x7c/0x130 arch/x86/kernel/irq.c:250
 ret_from_intr+0x0/0x21

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15918 Comm: syz-executor.2 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================