macvtap: zerocopy: put page when fail to get all requested user pages

When get_user_pages_fast() fails to get all requested pages, we could not use
kfree_skb() to free it as it has not been put in the skb fragments. So we need
to call put_page() instead.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/net/macvtap.c

@@ -531,9 +531,11 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
 		num_pages = get_user_pages_fast(base, size, 0, &page[i]);
 		if ((num_pages != size) ||
-		    (num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags))
-			/* put_page is in skb free */
+		    (num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags)) {
+			for (i = 0; i < num_pages; i++)
+				put_page(page[i]);
 			return -EFAULT;
+		}
 		truesize = size * PAGE_SIZE;
 		skb->data_len += len;
 		skb->len += len;