[PATCH v2 2/2] vsock/virtio: avoid refilling the RX queue after teardown

[Weiming Shi <bestswngs@gmail.com>]

Commit b917507e5ad9 ("vsock/virtio: stop workers during the .remove()")
made the RX worker jump to its common exit when rx_run is clear.  That
exit still refills the RX queue when the buffer count is low, so work
queued across virtio_vsock_vqs_del() can add buffers after the virtqueues
have been deleted.

BUG: KASAN: slab-use-after-free in virtqueue_add_sgs
Read of size 4 by task kworker/0:1
Workqueue: virtio_vsock virtio_transport_rx_work
Call Trace:
 virtqueue_add_sgs (drivers/virtio/virtio_ring.c:2796)
 virtio_vsock_rx_fill (net/vmw_vsock/virtio_transport.c:332)
 virtio_transport_rx_work (net/vmw_vsock/virtio_transport.c:701)
 process_one_work (kernel/workqueue.c:3314)
 worker_thread (kernel/workqueue.c:3478)
 kthread (kernel/kthread.c:436)
 ret_from_fork (arch/x86/kernel/process.c:158)
 ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
...
Freed by task 141:
 kfree (mm/slub.c:6566)
 vp_del_vq (drivers/virtio/virtio_pci_common.c:259)
 vp_del_vqs (drivers/virtio/virtio_pci_common.c:285)
 virtio_vsock_freeze (net/vmw_vsock/virtio_transport.c:912)
 virtio_device_freeze (drivers/virtio/virtio.c:658)
 virtio_pci_freeze (drivers/virtio/virtio_pci_common.c:601)
 pci_pm_freeze (drivers/pci/pci-driver.c:1098)
 device_suspend (drivers/base/power/main.c:1968)
Kernel panic - not syncing: KASAN: panic_on_warn set ...

Jump to a no-refill exit when rx_run is clear, leaving the normal exit
to replenish a running queue.

Fixes: b917507e5ad9 ("vsock/virtio: stop workers during the .remove()")
Cc: stable@vger.kernel.org
Reported-by: Xiang Mei <xmei5@asu.edu>
Link: https://lore.kernel.org/r/20260727035804.1860862-1-bestswngs@gmail.com
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Assisted-by: OpenAI-Codex:gpt-5
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
 net/vmw_vsock/virtio_transport.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index a8e1dd95ba8c..96c9fe8d357c 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -638,7 +638,7 @@ static void virtio_transport_rx_work(struct work_struct *work)
 	mutex_lock(&vsock->rx_lock);
 
 	if (!vsock->rx_run)
-		goto out;
+		goto out_nofill;
 
 	vq = vsock->vqs[VSOCK_VQ_RX];
 
@@ -692,6 +692,7 @@ static void virtio_transport_rx_work(struct work_struct *work)
 out:
 	if (vsock->rx_buf_nr < vsock->rx_buf_max_nr / 2)
 		virtio_vsock_rx_fill(vsock);
+out_nofill:
 	mutex_unlock(&vsock->rx_lock);
 }
 
-- 
2.55.0