net/mlx5e: Fix use-after-free after xdp_return_frame

[ Upstream commit 12fc512f ]

xdp_return_frame releases the frame. It leads to releasing the page, so
it's not allowed to access xdpi.xdpf->len after that, because xdpi.xdpf
is at xdp->data_hard_start after convert_to_xdp_frame. This patch moves
the memory access to precede the return of the frame.

Fixes: 58b99ee3 ("net/mlx5e: Add support for XDP_REDIRECT in device-out side")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c

@@ -227,9 +227,9 @@ bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq *cq)
 			sqcc++;
 
 			if (is_redirect) {
-				xdp_return_frame(xdpi->xdpf);
 				dma_unmap_single(sq->pdev, xdpi->dma_addr,
 						 xdpi->xdpf->len, DMA_TO_DEVICE);
+				xdp_return_frame(xdpi->xdpf);
 			} else {
 				/* Recycle RX page */
 				mlx5e_page_release(rq, &xdpi->di, true);
@@ -263,9 +263,9 @@ void mlx5e_free_xdpsq_descs(struct mlx5e_xdpsq *sq)
 		sq->cc++;
 
 		if (is_redirect) {
-			xdp_return_frame(xdpi->xdpf);
 			dma_unmap_single(sq->pdev, xdpi->dma_addr,
 					 xdpi->xdpf->len, DMA_TO_DEVICE);
+			xdp_return_frame(xdpi->xdpf);
 		} else {
 			/* Recycle RX page */
 			mlx5e_page_release(rq, &xdpi->di, false);