vhost: fail early when __vhost_add_used() fails

jasowang · mstsirkin · commit b4ba1207d45a · 2025-08-01T09:11:09.000-04:00
This patch fails vhost_add_used_n() early when __vhost_add_used()
fails to make sure used idx is not updated with stale used ring
information.

Reported-by: Eugenio Pérez &lt;eperezma@redhat.com&gt;
Signed-off-by: Jason Wang &lt;jasowang@redhat.com&gt;
Message-Id: &lt;20250714084755.11921-2-jasowang@redhat.com&gt;
Signed-off-by: Michael S. Tsirkin &lt;mst@redhat.com&gt;
Tested-by: Lei Yang &lt;leiyang@redhat.com&gt;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
@@ -2983,6 +2983,9 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
 	}
 	r = __vhost_add_used_n(vq, heads, count);
 
+	if (r < 0)
+		return r;
+
 	/* Make sure buffer is written before we update index. */
 	smp_wmb();
 	if (vhost_put_used_idx(vq)) {

Original file line number	Diff line number	Diff line change
`@@ -2983,6 +2983,9 @@ int vhost_add_used_n(struct vhost_virtqueue vq, struct vring_used_elem heads,`
`2983`	`2983`	`}`
`2984`	`2984`	`r = __vhost_add_used_n(vq, heads, count);`
`2985`	`2985`
	`2986`	`+ if (r < 0)`
	`2987`	`+ return r;`
	`2988`	`+`
`2986`	`2989`	`/* Make sure buffer is written before we update index. */`
`2987`	`2990`	`smp_wmb();`
`2988`	`2991`	`if (vhost_put_used_idx(vq)) {`