[dpdk-stable] [v18.11 PATCH v2 1/2] vhost: fix possible denial of service on SET_VRING_NUM

[Maxime Coquelin <maxime.coquelin@redhat.com>]

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

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost_user.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 5552f8bbfb..457e62d97e 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -346,6 +346,8 @@ 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) {
@@ -358,6 +360,8 @@ 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),
@@ -369,6 +373,8 @@ 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);
@@ -379,6 +385,8 @@ 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);
-- 
2.21.0