linux-kernel - [PATCH 4.19 098/100] net/mlx5e: Fix use-after-free after xdp_return

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Date:   Tue, 30 Apr 2019 13:39:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Maxim Mikityanskiy <maximmi@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [PATCH 4.19 098/100] net/mlx5e: Fix use-after-free after xdp_return_frame

From: Maxim Mikityanskiy <maximmi@...lanox.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 <maximmi@...lanox.com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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
@@ -227,9 +227,9 @@ bool mlx5e_poll_xdpsq_cq(struct mlx5e_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
 		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);