mlx4_core: Avoid vunmap() of invalid pointer if allocation fails

Signed-off-by: Ali Ayoub <ali@mellanox.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/net/mlx4/alloc.c

@@ -178,6 +178,7 @@ int mlx4_buf_alloc(struct mlx4_dev *dev, int size, int max_direct,
 	} else {
 		int i;
 
+		buf->direct.buf  = NULL;
 		buf->nbufs       = (size + PAGE_SIZE - 1) / PAGE_SIZE;
 		buf->npages      = buf->nbufs;
 		buf->page_shift  = PAGE_SHIFT;
@@ -229,7 +230,7 @@ void mlx4_buf_free(struct mlx4_dev *dev, int size, struct mlx4_buf *buf)
 		dma_free_coherent(&dev->pdev->dev, size, buf->direct.buf,
 				  buf->direct.map);
 	else {
-		if (BITS_PER_LONG == 64)
+		if (BITS_PER_LONG == 64 && buf->direct.buf)
 			vunmap(buf->direct.buf);
 
 		for (i = 0; i < buf->nbufs; ++i)