Subject: [PATCH] dmaengine: at_hdmac: fix potential NULL pointer dereference in atc_prep_dma_interleaved

From: [email-masked] (Gustavo A. R. Silva)
Date: Mon, 20 Nov 2017 08:28:14 -0600

_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 <[email-masked]>
---
 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 fbab271..a861b5b 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -708,7 +708,7 @@ 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;
@@ -720,6 +720,8 @@ 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,
-- 
2.7.4