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BUG: KCSAN: data-race in virtqueue_enable_cb_delayed / virtqueue_enable_cb_prepare

read to 0xffff8881290b07f0 of 2 bytes by task 7951 on cpu 1:
 virtqueue_enable_cb_delayed_split drivers/virtio/virtio_ring.c:794 [inline]
 virtqueue_enable_cb_delayed+0x1dc/0x4d0 drivers/virtio/virtio_ring.c:2006
 start_xmit+0xb0f/0xbe0 drivers/net/virtio_net.c:1565
 __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_cleanup_rbuf+0x130/0x360 net/ipv4/tcp.c:1578
 tcp_recvmsg+0x687/0x1c90 net/ipv4/tcp.c:2184
 inet_recvmsg+0xbb/0x250 net/ipv4/af_inet.c:838
 sock_recvmsg_nosec net/socket.c:873 [inline]
 sock_recvmsg net/socket.c:891 [inline]
 sock_recvmsg+0x92/0xb0 net/socket.c:887
 sock_read_iter+0x15f/0x1e0 net/socket.c:969
 call_read_iter include/linux/fs.h:1896 [inline]
 new_sync_read+0x4b1/0x4f0 fs/read_write.c:414
 __vfs_read+0xb1/0xc0 fs/read_write.c:427
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x143/0x2c0 fs/read_write.c:446
 ksys_read+0x17b/0x1b0 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read fs/read_write.c:595 [inline]
 __x64_sys_read+0x4c/0x60 fs/read_write.c:595
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881290b07f0 of 2 bytes by interrupt on cpu 0:
 virtqueue_enable_cb_prepare_split drivers/virtio/virtio_ring.c:762 [inline]
 virtqueue_enable_cb_prepare+0x1ce/0x2b0 drivers/virtio/virtio_ring.c:1946
 virtqueue_napi_complete+0x2c/0xa0 drivers/net/virtio_net.c:328
 virtnet_poll_tx+0x15f/0x1d0 drivers/net/virtio_net.c:1496
 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_enable arch/x86/include/asm/paravirt.h:762 [inline]
 preempt_schedule_irq+0x4d/0x90 kernel/sched/core.c:4337
 restore_regs_and_return_to_kernel+0x0/0x25
 __sanitizer_cov_trace_pc+0x32/0x50 kernel/kcov.c:190
 compound_head include/linux/page-flags.h:174 [inline]
 PageSwapBacked include/linux/page-flags.h:340 [inline]
 PageSwapCache include/linux/page-flags.h:385 [inline]
 page_mapping+0x119/0x2a0 mm/util.c:668
 __test_set_page_writeback+0x41/0x7d0 mm/page-writeback.c:2766
 set_page_writeback include/linux/page-flags.h:542 [inline]
 __block_write_full_page+0x46b/0x870 fs/buffer.c:1802
 block_write_full_page+0x1c0/0x1e0 fs/buffer.c:2993
 blkdev_writepage+0x2e/0x40 fs/block_dev.c:609
 __writepage+0x40/0xb0 mm/page-writeback.c:2303
 write_cache_pages+0x47a/0xb40 mm/page-writeback.c:2238
 generic_writepages mm/page-writeback.c:2329 [inline]
 generic_writepages+0x79/0xc0 mm/page-writeback.c:2318
 blkdev_writepages+0x27/0x40 fs/block_dev.c:2060
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1c5/0x230 mm/filemap.c:421
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x2d/0x40 mm/filemap.c:456
 __sync_blockdev fs/block_dev.c:490 [inline]
 __sync_blockdev+0x81/0x90 fs/block_dev.c:485
 __sync_filesystem fs/sync.c:40 [inline]
 sync_filesystem+0x116/0x1a0 fs/sync.c:64
 __do_sys_syncfs fs/sync.c:171 [inline]
 __se_sys_syncfs fs/sync.c:160 [inline]
 __x64_sys_syncfs+0x80/0xd0 fs/sync.c:160
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4657 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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