[PATCH 5.0 87/89] net/mlx5e: Fix use-after-free after xdp_return_frame

[Greg Kroah-Hartman]

From: Maxim Mikityanskiy <maxi...@mellanox.com>

[ Upstream commit 12fc512f5741443a03adde2ead20724da8ad550a ]

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: 58b99ee3e3ebe ("net/mlx5e: Add support for XDP_REDIRECT in device-out 
side")
Signed-off-by: Maxim Mikityanskiy <maxi...@mellanox.com>
Signed-off-by: Saeed Mahameed <sae...@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -324,9 +324,9 @@ bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq
                                        mlx5e_xdpi_fifo_pop(xdpi_fifo);
 
                                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);
@@ -365,9 +365,9 @@ void mlx5e_free_xdpsq_descs(struct mlx5e
                                mlx5e_xdpi_fifo_pop(xdpi_fifo);
 
                        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);