staging: mt7621-dma: fix potentially dereferencing uninitialized 'tx_desc'

Function 'mtk_hsdma_start_transfer' uses 'tx_desc' pointer which can be
dereferenced before it is initializated. Initializate pointer before
avoiding the problem.

Fixes: 0853c7a53eb3 ("staging: mt7621-dma: ralink: add rt2880 dma engine")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/mt7621-dma/mtk-hsdma.c b/drivers/staging/mt7621-dma/mtk-hsdma.c
index df6ebf41bdea4dc7301414c5cb9b42e5679d5472..5831f816c17b1d37c86b3c332aeff2305930c117 100644 (file)
--- a/drivers/staging/mt7621-dma/mtk-hsdma.c
+++ b/drivers/staging/mt7621-dma/mtk-hsdma.c
@@ -335,6 +335,8 @@ static int mtk_hsdma_start_transfer(struct mtk_hsdam_engine *hsdma,
        /* tx desc */
        src = sg->src_addr;
        for (i = 0; i < chan->desc->num_sgs; i++) {
+               tx_desc = &chan->tx_ring[chan->tx_idx];
+
                if (len > HSDMA_MAX_PLEN)
                        tlen = HSDMA_MAX_PLEN;
                else
@@ -344,7 +346,6 @@ static int mtk_hsdma_start_transfer(struct mtk_hsdam_engine *hsdma,
                        tx_desc->addr1 = src;
                        tx_desc->flags |= HSDMA_DESC_PLEN1(tlen);
                } else {
-                       tx_desc = &chan->tx_ring[chan->tx_idx];
                        tx_desc->addr0 = src;
                        tx_desc->flags = HSDMA_DESC_PLEN0(tlen);