linux-kernel - [PATCH 1/4] dmaengine: zynqmp_dma: Typecast the variable to handle overflow

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Date:   Tue, 14 Sep 2021 13:58:14 +0530
From:   Harini Katakam <harini.katakam@...inx.com>
To:     <vkoul@...nel.org>, <romain.perier@...il.com>,
        <allen.lkml@...il.com>, <yukuai3@...wei.com>
CC:     <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <harinikatakamlinux@...il.com>,
        <michal.simek@...inx.com>, <harini.katakam@...inx.com>,
        <radhey.shyam.pandey@...inx.com>, <shravya.kumbham@...inx.com>
Subject: [PATCH 1/4] dmaengine: zynqmp_dma: Typecast the variable to handle overflow

From: Shravya Kumbham <shravya.kumbham@...inx.com>

In zynqmp_dma_alloc/free_chan_resources functions there is a
potential overflow in the below expressions.

dma_alloc_coherent(chan->dev, (2 * chan->desc_size *
		   ZYNQMP_DMA_NUM_DESCS),
		   &chan->desc_pool_p, GFP_KERNEL);

dma_free_coherent(chan->dev,(2 * ZYNQMP_DMA_DESC_SIZE(chan) *
                 ZYNQMP_DMA_NUM_DESCS),
                chan->desc_pool_v, chan->desc_pool_p);

The arguments desc_size and ZYNQMP_DMA_NUM_DESCS are 32 bit. Though
this overflow condition is not observed but it is a potential problem
in the case of 32-bit multiplication. Hence fix it by using typecast.

Addresses-Coverity: Event overflow_before_widen.
Signed-off-by: Shravya Kumbham <shravya.kumbham@...inx.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>
---
 drivers/dma/xilinx/zynqmp_dma.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index 5fecf5aa6e85..2d0eba25739d 100644
--- a/drivers/dma/xilinx/zynqmp_dma.c
+++ b/drivers/dma/xilinx/zynqmp_dma.c
@@ -490,7 +490,8 @@ static int zynqmp_dma_alloc_chan_resources(struct dma_chan *dchan)
 	}
 
 	chan->desc_pool_v = dma_alloc_coherent(chan->dev,
-					       (2 * chan->desc_size * ZYNQMP_DMA_NUM_DESCS),
+					       ((size_t)(2 * chan->desc_size) *
+						ZYNQMP_DMA_NUM_DESCS),
 					       &chan->desc_pool_p, GFP_KERNEL);
 	if (!chan->desc_pool_v)
 		return -ENOMEM;
@@ -677,7 +678,8 @@ static void zynqmp_dma_free_chan_resources(struct dma_chan *dchan)
 	zynqmp_dma_free_descriptors(chan);
 	spin_unlock_irqrestore(&chan->lock, irqflags);
 	dma_free_coherent(chan->dev,
-		(2 * ZYNQMP_DMA_DESC_SIZE(chan) * ZYNQMP_DMA_NUM_DESCS),
+		((size_t)(2 * ZYNQMP_DMA_DESC_SIZE(chan)) *
+		 ZYNQMP_DMA_NUM_DESCS),
 		chan->desc_pool_v, chan->desc_pool_p);
 	kfree(chan->sw_desc_pool);
 	pm_runtime_mark_last_busy(chan->dev);
-- 
2.17.1