[PULL v4 47/48] libvhost-user: return early on virtqueue errors

["Michael S. Tsirkin" <mst@redhat.com>]

From: Stefan Hajnoczi <stefanha@redhat.com>

vu_panic() is not guaranteed to exit the program. Return early when
errors are encountered.

Note that libvhost-user does not have an "unmap" operation for mapped
descriptors. Therefore it is correct to return without explicit cleanup.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200921113420.154378-2-stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 contrib/libvhost-user/libvhost-user.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index 70055c98b7..4ebfa4cc40 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -2416,7 +2416,7 @@ vu_queue_set_notification(VuDev *dev, VuVirtq *vq, int enable)
     }
 }
 
-static void
+static bool
 virtqueue_map_desc(VuDev *dev,
                    unsigned int *p_num_sg, struct iovec *iov,
                    unsigned int max_num_sg, bool is_write,
@@ -2428,7 +2428,7 @@ virtqueue_map_desc(VuDev *dev,
 
     if (!sz) {
         vu_panic(dev, "virtio: zero sized buffers are not allowed");
-        return;
+        return false;
     }
 
     while (sz) {
@@ -2436,13 +2436,13 @@ virtqueue_map_desc(VuDev *dev,
 
         if (num_sg == max_num_sg) {
             vu_panic(dev, "virtio: too many descriptors in indirect table");
-            return;
+            return false;
         }
 
         iov[num_sg].iov_base = vu_gpa_to_va(dev, &len, pa);
         if (iov[num_sg].iov_base == NULL) {
             vu_panic(dev, "virtio: invalid address for buffers");
-            return;
+            return false;
         }
         iov[num_sg].iov_len = len;
         num_sg++;
@@ -2451,6 +2451,7 @@ virtqueue_map_desc(VuDev *dev,
     }
 
     *p_num_sg = num_sg;
+    return true;
 }
 
 static void *
@@ -2488,6 +2489,7 @@ vu_queue_map_desc(VuDev *dev, VuVirtq *vq, unsigned int idx, size_t sz)
     if (lduw_le_p(&desc[i].flags) & VRING_DESC_F_INDIRECT) {
         if (ldl_le_p(&desc[i].len) % sizeof(struct vring_desc)) {
             vu_panic(dev, "Invalid size for indirect buffer table");
+            return NULL;
         }
 
         /* loop over the indirect descriptor table */
@@ -2515,22 +2517,29 @@ vu_queue_map_desc(VuDev *dev, VuVirtq *vq, unsigned int idx, size_t sz)
     /* Collect all the descriptors */
     do {
         if (lduw_le_p(&desc[i].flags) & VRING_DESC_F_WRITE) {
-            virtqueue_map_desc(dev, &in_num, iov + out_num,
+            if (!virtqueue_map_desc(dev, &in_num, iov + out_num,
                                VIRTQUEUE_MAX_SIZE - out_num, true,
-                               ldq_le_p(&desc[i].addr), ldl_le_p(&desc[i].len));
+                               ldq_le_p(&desc[i].addr),
+                               ldl_le_p(&desc[i].len))) {
+                return NULL;
+            }
         } else {
             if (in_num) {
                 vu_panic(dev, "Incorrect order for descriptors");
                 return NULL;
             }
-            virtqueue_map_desc(dev, &out_num, iov,
+            if (!virtqueue_map_desc(dev, &out_num, iov,
                                VIRTQUEUE_MAX_SIZE, false,
-                               ldq_le_p(&desc[i].addr), ldl_le_p(&desc[i].len));
+                               ldq_le_p(&desc[i].addr),
+                               ldl_le_p(&desc[i].len))) {
+                return NULL;
+            }
         }
 
         /* If we've got too many, that implies a descriptor loop. */
         if ((in_num + out_num) > max) {
             vu_panic(dev, "Looped descriptor");
+            return NULL;
         }
         rc = virtqueue_read_next_desc(dev, desc, i, max, &i);
     } while (rc == VIRTQUEUE_READ_DESC_MORE);
-- 
MST