netdev - [net 1/3] net/mlx5e: Fix use-after-free after xdp_return

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Message-Id: <20190419210312.19338-2-saeedm@mellanox.com>
Date:   Fri, 19 Apr 2019 14:03:10 -0700
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Maxim Mikityanskiy <maximmi@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [net 1/3] net/mlx5e: Fix use-after-free after xdp_return_frame

From: Maxim Mikityanskiy <maximmi@...lanox.com>

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>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index 03b2a9f9c589..10a99cd3e598 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -304,9 +304,9 @@ bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq *cq, struct mlx5e_rq *rq)
 					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);
@@ -345,9 +345,9 @@ void mlx5e_free_xdpsq_descs(struct mlx5e_xdpsq *sq, struct mlx5e_rq *rq)
 				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);
-- 
2.20.1