vhost: relax used address alignment
authorMichael S. Tsirkin <mst@redhat.com>
Sat, 20 Dec 2014 23:00:23 +0000 (01:00 +0200)
committerMichael S. Tsirkin <mst@redhat.com>
Mon, 29 Dec 2014 08:55:06 +0000 (10:55 +0200)
virtio 1.0 only requires used address to be 4 byte aligned,
vhost required 8 bytes (size of vring_used_elem).
Fix up vhost to match that.

Additionally, while vhost correctly requires 8 byte
alignment for log, it's unconnected to used ring:
it's a consequence that log has u64 entries.
Tweak code to make that clearer.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
drivers/vhost/vhost.c

index ed71b5347a766ee26c95039638a028ece31b53de..cb807d0ea498df3a197d0c3ed70d5548e57d97b7 100644 (file)
@@ -713,9 +713,13 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
                        r = -EFAULT;
                        break;
                }
-               if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
-                   (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
-                   (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
+
+               /* Make sure it's safe to cast pointers to vring types. */
+               BUILD_BUG_ON(__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE);
+               BUILD_BUG_ON(__alignof__ *vq->used > VRING_USED_ALIGN_SIZE);
+               if ((a.avail_user_addr & (VRING_AVAIL_ALIGN_SIZE - 1)) ||
+                   (a.used_user_addr & (VRING_USED_ALIGN_SIZE - 1)) ||
+                   (a.log_guest_addr & (sizeof(u64) - 1))) {
                        r = -EINVAL;
                        break;
                }