virtio: fix oops on OOM

virtio ring was changed to return an error code on OOM, but one caller was missed and still checks for vq->vring.num. The fix is just to check for <0 error code. Long term it might make sense to change goto add_head to just return an error on oom instead, but let's apply a minimal fix for 2.6.35. Reported-by: Chris Mason <[email protected]> Signed-off-by: Michael S. Tsirkin <[email protected]> Signed-off-by: Rusty Russell <[email protected]> Tested-by: Chris Mason <[email protected]> Cc: [email protected] # .34.x Signed-off-by: Linus Torvalds <[email protected]>
mrcsosa · Jul 26, 2010 · 1fe9b6f · 1fe9b6f
1 parent 2e65a20
commit 1fe9b6f
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
@@ -164,7 +164,8 @@ int virtqueue_add_buf_gfp(struct virtqueue *_vq,
 			  gfp_t gfp)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
-	unsigned int i, avail, head, uninitialized_var(prev);
+	unsigned int i, avail, uninitialized_var(prev);
+	int head;
 
 	START_USE(vq);
 
@@ -174,7 +175,7 @@ int virtqueue_add_buf_gfp(struct virtqueue *_vq,
 	 * buffers, then go indirect. FIXME: tune this threshold */
 	if (vq->indirect && (out + in) > 1 && vq->num_free) {
 		head = vring_add_indirect(vq, sg, out, in, gfp);
-		if (head != vq->vring.num)
+		if (likely(head >= 0))
 			goto add_head;
 	}