linux-kernel - [PATCH v3 7/8] platform: sh_veu: use 64-bit arithmetic instead of 32-bit

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Message-ID: <502e55a2fd44a61126b639d581c8fa7447eb0e72.1517929336.git.gustavo@embeddedor.com>
Date:   Tue, 6 Feb 2018 10:52:24 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: [PATCH v3 7/8] platform: sh_veu: use 64-bit arithmetic instead of
 32-bit

Cast left and top to dma_addr_t in order to give the compiler complete
information about the proper arithmetic to use. Notice that these
variables are being used in contexts that expect expressions of
type dma_addr_t (64 bit, unsigned).

Such expressions are currently being evaluated using 32-bit arithmetic.

Also, move the expression (((dma_addr_t)left * veu->vfmt_out.fmt->depth) >> 3)
at the end in order to avoid a line wrapping checkpatch.pl warning.

Addresses-Coverity-ID: 1056807 ("Unintentional integer overflow")
Addresses-Coverity-ID: 1056808 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
Changes in v2:
 - Update subject and changelog to better reflect the proposed code changes.
 - Move the expression (((dma_addr_t)left * veu->vfmt_out.fmt->depth) >> 3)
   at the end in order to avoid a line wrapping checkpatch.pl warning.

Changes in v3:
 - Mention the specific Coverity reports in the commit message.

 drivers/media/platform/sh_veu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/sh_veu.c b/drivers/media/platform/sh_veu.c
index 976ea0b..1a0cde0 100644
--- a/drivers/media/platform/sh_veu.c
+++ b/drivers/media/platform/sh_veu.c
@@ -520,8 +520,8 @@ static void sh_veu_colour_offset(struct sh_veu_dev *veu, struct sh_veu_vfmt *vfm
 	/* dst_left and dst_top validity will be verified in CROP / COMPOSE */
 	unsigned int left = vfmt->frame.left & ~0x03;
 	unsigned int top = vfmt->frame.top;
-	dma_addr_t offset = ((left * veu->vfmt_out.fmt->depth) >> 3) +
-		top * veu->vfmt_out.bytesperline;
+	dma_addr_t offset = (dma_addr_t)top * veu->vfmt_out.bytesperline +
+			(((dma_addr_t)left * veu->vfmt_out.fmt->depth) >> 3);
 	unsigned int y_line;
 
 	vfmt->offset_y = offset;
-- 
2.7.4