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BUG: KCSAN: data-race in detach_buf_split / virtqueue_add

read to 0xffff88810146fe48 of 4 bytes by task 30609 on cpu 0:
 virtqueue_add_split drivers/virtio/virtio_ring.c:553 [inline]
 virtqueue_add+0x4b3/0x20e0 drivers/virtio/virtio_ring.c:2133
 virtqueue_add_inbuf+0x53/0x80 drivers/virtio/virtio_ring.c:2212
 request_entropy drivers/char/hw_random/virtio-rng.c:61 [inline]
 copy_data drivers/char/hw_random/virtio-rng.c:74 [inline]
 virtio_read+0x1c5/0x3f0 drivers/char/hw_random/virtio-rng.c:92
 rng_get_data drivers/char/hw_random/core.c:197 [inline]
 rng_dev_read+0x1a7/0x5e0 drivers/char/hw_random/core.c:234
 vfs_read+0x19f/0x5c0 fs/read_write.c:468
 ksys_read+0xeb/0x1a0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:621
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read-write to 0xffff88810146fe48 of 4 bytes by interrupt on cpu 1:
 detach_buf_split+0x2fc/0x570 drivers/virtio/virtio_ring.c:757
 virtqueue_get_buf_ctx_split drivers/virtio/virtio_ring.c:835 [inline]
 virtqueue_get_buf_ctx+0x3c2/0x5b0 drivers/virtio/virtio_ring.c:2327
 virtqueue_get_buf+0x1f/0x30 drivers/virtio/virtio_ring.c:2333
 random_recv_done+0x4c/0x90 drivers/char/hw_random/virtio-rng.c:42
 vring_interrupt+0x150/0x170 drivers/virtio/virtio_ring.c:2501
 __handle_irq_event_percpu+0x91/0x490 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0x64/0xf0 kernel/irq/handle.c:210
 handle_edge_irq+0x167/0x590 kernel/irq/chip.c:834
 generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
 handle_irq arch/x86/kernel/irq.c:238 [inline]
 __common_interrupt+0x3c/0xb0 arch/x86/kernel/irq.c:257
 common_interrupt+0x7a/0x90 arch/x86/kernel/irq.c:247
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636
 batadv_hardif_get_by_netdev net/batman-adv/hard-interface.c:71 [inline]
 batadv_hard_if_event+0xa6/0x10c0 net/batman-adv/hard-interface.c:949
 notifier_call_chain kernel/notifier.c:93 [inline]
 raw_notifier_call_chain+0x6b/0x1c0 kernel/notifier.c:461
 call_netdevice_notifiers_info net/core/dev.c:1935 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:1973 [inline]
 call_netdevice_notifiers+0xc8/0x130 net/core/dev.c:1987
 register_netdevice+0xb37/0xcd0 net/core/dev.c:10120
 __ip_tunnel_create+0x1c5/0x260 net/ipv4/ip_tunnel.c:267
 ip_tunnel_init_net+0x183/0x3c0 net/ipv4/ip_tunnel.c:1091
 ipgre_init_net+0x30/0x40 net/ipv4/ip_gre.c:1020
 ops_init+0x1fc/0x2c0 net/core/net_namespace.c:136
 setup_net+0x2b5/0x700 net/core/net_namespace.c:339
 copy_net_ns+0x36c/0x500 net/core/net_namespace.c:491
 create_new_namespaces+0x228/0x430 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xe4/0x120 kernel/nsproxy.c:228
 ksys_unshare+0x38d/0x6d0 kernel/fork.c:3441
 __do_sys_unshare kernel/fork.c:3512 [inline]
 __se_sys_unshare kernel/fork.c:3510 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3510
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30606 Comm: syz-executor.2 Not tainted 6.4.0-syzkaller-01371-g04fc8904d5d1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
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virtio_rng virtio3: input:id 0 is not a head!