[moderation] [virt?] KCSAN: data-race in virtqueue_disable_cb / virtqueue_enable_cb_delayed (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8e621c9a3375 Merge tag 'net-6.18-rc7' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13368c2a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=655255e3ef31c19b
dashboard link: https://syzkaller.appspot.com/bug?extid=911d0216df4f6ff1a9b8
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [eper...@redhat.com jaso...@redhat.com linux-...@vger.kernel.org m...@redhat.com virtual...@lists.linux.dev xuan...@linux.alibaba.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3fa2a952c73d/disk-8e621c9a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/69e8f3222893/vmlinux-8e621c9a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b395535db1d4/bzImage-8e621c9a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+911d02...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in virtqueue_disable_cb / virtqueue_enable_cb_delayed

write to 0xffff888102048f78 of 2 bytes by task 3305 on cpu 1:
virtqueue_enable_cb_delayed_split drivers/virtio/virtio_ring.c:943 [inline]
virtqueue_enable_cb_delayed+0x116/0x380 drivers/virtio/virtio_ring.c:2659
start_xmit+0x1357/0x17a0 drivers/net/virtio_net.c:3423
__netdev_start_xmit include/linux/netdevice.h:5248 [inline]
netdev_start_xmit include/linux/netdevice.h:5257 [inline]
xmit_one net/core/dev.c:3845 [inline]
dev_hard_start_xmit+0x125/0x3e0 net/core/dev.c:3861
sch_direct_xmit+0x192/0x550 net/sched/sch_generic.c:347
__dev_xmit_skb net/core/dev.c:4152 [inline]
__dev_queue_xmit+0xe9a/0x2000 net/core/dev.c:4729
dev_queue_xmit include/linux/netdevice.h:3365 [inline]
neigh_hh_output include/net/neighbour.h:531 [inline]
neigh_output include/net/neighbour.h:545 [inline]
ip_finish_output2+0x77f/0x8b0 net/ipv4/ip_output.c:237
__ip_finish_output net/ipv4/ip_output.c:-1 [inline]
ip_finish_output+0x114/0x2a0 net/ipv4/ip_output.c:325
NF_HOOK_COND include/linux/netfilter.h:307 [inline]
ip_output+0xbd/0x190 net/ipv4/ip_output.c:438
dst_output include/net/dst.h:464 [inline]
ip_local_out net/ipv4/ip_output.c:131 [inline]
__ip_queue_xmit+0xbbf/0xc00 net/ipv4/ip_output.c:534
ip_queue_xmit+0x39/0x50 net/ipv4/ip_output.c:548
__tcp_transmit_skb+0x17fd/0x1c10 net/ipv4/tcp_output.c:1628
tcp_transmit_skb net/ipv4/tcp_output.c:1646 [inline]
tcp_write_xmit+0x129c/0x30f0 net/ipv4/tcp_output.c:2999
tcp_push_one+0x7e/0xa0 net/ipv4/tcp_output.c:3196
tcp_sendmsg_locked+0x1cd0/0x2c00 net/ipv4/tcp.c:1356
tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1413
inet_sendmsg+0x76/0xd0 net/ipv4/af_inet.c:853
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x102/0x180 net/socket.c:742
sock_write_iter+0x1a7/0x1f0 net/socket.c:1195
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x52a/0x960 fs/read_write.c:686
ksys_write+0xda/0x1a0 fs/read_write.c:738
__do_sys_write fs/read_write.c:749 [inline]
__se_sys_write fs/read_write.c:746 [inline]
__x64_sys_write+0x40/0x50 fs/read_write.c:746
x64_sys_call+0x2802/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888102048f78 of 2 bytes by interrupt on cpu 0:
virtqueue_disable_cb_split drivers/virtio/virtio_ring.c:877 [inline]
virtqueue_disable_cb+0x58/0x150 drivers/virtio/virtio_ring.c:2569
skb_xmit_done+0x65/0x140 drivers/net/virtio_net.c:784
vring_interrupt+0x155/0x180 drivers/virtio/virtio_ring.c:2718
__handle_irq_event_percpu+0x9d/0x540 kernel/irq/handle.c:203
handle_irq_event_percpu kernel/irq/handle.c:240 [inline]
handle_irq_event+0x64/0xf0 kernel/irq/handle.c:257
handle_edge_irq+0x154/0x470 kernel/irq/chip.c:855
generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
handle_irq arch/x86/kernel/irq.c:254 [inline]
call_irq_handler arch/x86/kernel/irq.c:-1 [inline]
__common_interrupt+0x60/0xb0 arch/x86/kernel/irq.c:325
common_interrupt+0x7e/0x90 arch/x86/kernel/irq.c:318
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:81
arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
default_idle+0x13/0x20 arch/x86/kernel/process.c:767
default_idle_call+0x3c/0x60 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:190 [inline]
do_idle+0xcb/0x240 kernel/sched/idle.c:330
cpu_startup_entry+0x25/0x30 kernel/sched/idle.c:428
rest_init+0xee/0xf0 init/main.c:757
start_kernel+0x4dc/0x510 init/main.c:1111
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0xfc/0x100 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x147

value changed: 0x0001 -> 0x0000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================


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