[dpdk-dev] [PATCH v3 2/2] vhost: do sanity check for ring descriptor address

[Ilya Maximets]

In current implementation vhost will crash with segmentation fault
if malicious or buggy virtio application breaks addresses of descriptors.

Before commit 0823c1cb0a73 ("vhost: workaround stale vring base")
this crash was reproducible even with normal DPDK application that tries
to change number of virtqueues dynamically inside VM.

Fix that by checking addresses of descriptors before using.

Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
---
 lib/librte_vhost/vhost_rxtx.c | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index a9b04df..bc00518 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -147,10 +147,15 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
        struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};

        desc = &vq->desc[desc_idx];
-       if (unlikely(desc->len < dev->vhost_hlen))
+       desc_addr = gpa_to_vva(dev, desc->addr);
+       /*
+        * Checking of 'desc_addr' placed outside of 'unlikely' macro to avoid
+        * performance issue with some versions of gcc (4.8.4 and 5.3.0) which
+        * otherwise stores offset on the stack instead of in a register.
+        */
+       if (unlikely(desc->len < dev->vhost_hlen) || !desc_addr)
                return -1;

-       desc_addr = gpa_to_vva(dev, desc->addr);
        rte_prefetch0((void *)(uintptr_t)desc_addr);

        virtio_enqueue_offload(m, &virtio_hdr.hdr);
@@ -182,7 +187,10 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
                                return -1;

                        desc = &vq->desc[desc->next];
-                       desc_addr   = gpa_to_vva(dev, desc->addr);
+                       desc_addr = gpa_to_vva(dev, desc->addr);
+                       if (unlikely(!desc_addr))
+                               return -1;
+
                        desc_offset = 0;
                        desc_avail  = desc->len;
                }
@@ -387,10 +395,10 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, 
struct vhost_virtqueue *vq,
        LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
                dev->vid, cur_idx, end_idx);

-       if (buf_vec[vec_idx].buf_len < dev->vhost_hlen)
+       desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
+       if (buf_vec[vec_idx].buf_len < dev->vhost_hlen || !desc_addr)
                return 0;

-       desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
        rte_prefetch0((void *)(uintptr_t)desc_addr);

        virtio_hdr.num_buffers = end_idx - start_idx;
@@ -425,6 +433,8 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct 
vhost_virtqueue *vq,

                        vec_idx++;
                        desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
+                       if (unlikely(!desc_addr))
+                               return 0;

                        /* Prefetch buffer address. */
                        rte_prefetch0((void *)(uintptr_t)desc_addr);
@@ -688,6 +698,9 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
                return -1;

        desc_addr = gpa_to_vva(dev, desc->addr);
+       if (unlikely(!desc_addr))
+               return -1;
+
        hdr = (struct virtio_net_hdr *)((uintptr_t)desc_addr);
        rte_prefetch0(hdr);

@@ -701,6 +714,9 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
                desc = &vq->desc[desc->next];

                desc_addr = gpa_to_vva(dev, desc->addr);
+               if (unlikely(!desc_addr))
+                       return -1;
+
                rte_prefetch0((void *)(uintptr_t)desc_addr);

                desc_offset = 0;
@@ -737,6 +753,9 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
                        desc = &vq->desc[desc->next];

                        desc_addr = gpa_to_vva(dev, desc->addr);
+                       if (unlikely(!desc_addr))
+                               return -1;
+
                        rte_prefetch0((void *)(uintptr_t)desc_addr);

                        desc_offset = 0;
-- 
2.7.4