vhost: fail early when __vhost_add_used() fails

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 <eperezma@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20250714084755.11921-2-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f4c1bc6adeda050639ce2ef983cfcb81b92a4d25..b38e39242fb9eb45a22169e095af2dbe1a360518 100644 (file)
--- 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)) {