linux-kernel - [PATCH AUTOSEL for 4.4 23/36] dmaengine: at_hdmac: fix potential NULL pointer dereference in atc_prep_dma

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Message-ID: <20180128222815.29479-23-alexander.levin@microsoft.com>
Date:   Sun, 28 Jan 2018 22:28:39 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Vinod Koul <vinod.koul@...el.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.4 23/36] dmaengine: at_hdmac: fix potential NULL
 pointer dereference in atc_prep_dma_interleaved

From: "Gustavo A. R. Silva" <garsilva@...eddedor.com>

[ Upstream commit 62a277d43d47e74972de44d33bd3763e31992414 ]

_xt_ is being dereferenced before it is null checked, hence there is a
potential null pointer dereference.

Fix this by moving the pointer dereference after _xt_ has been null
checked.

This issue was detected with the help of Coccinelle.

Fixes: 4483320e241c ("dmaengine: Use Pointer xt after NULL check.")
Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
Signed-off-by: Vinod Koul <vinod.koul@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/dma/at_hdmac.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 53d22eb73b56..be26f625bb3e 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -716,7 +716,7 @@ atc_prep_dma_interleaved(struct dma_chan *chan,
 			 unsigned long flags)
 {
 	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
-	struct data_chunk	*first = xt->sgl;
+	struct data_chunk	*first;
 	struct at_desc		*desc = NULL;
 	size_t			xfer_count;
 	unsigned int		dwidth;
@@ -728,6 +728,8 @@ atc_prep_dma_interleaved(struct dma_chan *chan,
 	if (unlikely(!xt || xt->numf != 1 || !xt->frame_size))
 		return NULL;
 
+	first = xt->sgl;
+
 	dev_info(chan2dev(chan),
 		 "%s: src=%pad, dest=%pad, numf=%d, frame_size=%d, flags=0x%lx\n",
 		__func__, &xt->src_start, &xt->dst_start, xt->numf,
-- 
2.11.0