vhost: fix possible denial of service on SET_VRING_NUM

vhost_user_set_vring_num() performs multiple allocations
without checking whether data were previously allocated.

It may cause a denial of service because of the memory leaks
that happen if a malicious vhost-user master keeps sending
VHOST_USER_SET_VRING_NUM request until the slave runs out
of memory.

This issue has been assigned CVE-2019-14818

Fixes: b0a985d1f340 ("vhost: add dequeue zero copy")
Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index cc660e03a88b98d87e2b44b42cd0a4d04c2c1fb3..d4c9cd3f290810b5697005ff0c818c6d12508bec 100644 (file)
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -386,6 +386,8 @@ vhost_user_set_vring_num(struct virtio_net **pdev,
                vq->nr_zmbuf = 0;
                vq->last_zmbuf_idx = 0;
                vq->zmbuf_size = vq->size;
+               if (vq->zmbufs)
+                       rte_free(vq->zmbufs);
                vq->zmbufs = rte_zmalloc(NULL, vq->zmbuf_size *
                                         sizeof(struct zcopy_mbuf), 0);
                if (vq->zmbufs == NULL) {
@@ -398,6 +400,8 @@ vhost_user_set_vring_num(struct virtio_net **pdev,
        }
 
        if (vq_is_packed(dev)) {
+               if (vq->shadow_used_packed)
+                       rte_free(vq->shadow_used_packed);
                vq->shadow_used_packed = rte_malloc(NULL,
                                vq->size *
                                sizeof(struct vring_used_elem_packed),
@@ -409,6 +413,8 @@ vhost_user_set_vring_num(struct virtio_net **pdev,
                }
 
        } else {
+               if (vq->shadow_used_split)
+                       rte_free(vq->shadow_used_split);
                vq->shadow_used_split = rte_malloc(NULL,
                                vq->size * sizeof(struct vring_used_elem),
                                RTE_CACHE_LINE_SIZE);
@@ -419,6 +425,8 @@ vhost_user_set_vring_num(struct virtio_net **pdev,
                }
        }
 
+       if (vq->batch_copy_elems)
+               rte_free(vq->batch_copy_elems);
        vq->batch_copy_elems = rte_malloc(NULL,
                                vq->size * sizeof(struct batch_copy_elem),
                                RTE_CACHE_LINE_SIZE);