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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Sylwester Nawrocki" <s.nawrocki@samsung.com>,
        "Mauro Carvalho Chehab" <mchehab@s-opensource.com>,
        "Arnd Bergmann" <arnd@arndb.de>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
Message-ID: <lsq.1528380321.535439802@decadent.org.uk>
Subject: [PATCH 3.16 087/410] media: exynos4-is: properly initialize frame
 format
In-Reply-To: <lsq.1528380320.647747352@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@arndb.de>

commit 97913bcbe6da3957af27d9fdd76b3d97b99e6d6a upstream.

We copy the subdev frame format from a partially initialized
structure, which is not entirely well-defined. Older compilers
like gcc-4.4 can copy uninitialized stack data here and warn
about it:

drivers/media/platform/exynos4-is/fimc-isp.c: In function 'fimc_isp_subdev_open':
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.reserved[10u]' may be used uninitialized in this function
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.reserved[9u]' may be used uninitialized in this function
...
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.reserved[0u]' may be used uninitialized in this function
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.xfer_func' may be used uninitialized in this function

On newer compilers, only the initialized fields get copied, but
we should not rely on that, so this changes the code to zero-out
the remaining fields first.

Fixes: 9a761e436843 ("[media] exynos4-is: Add Exynos4x12 FIMC-IS driver")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/media/platform/exynos4-is/fimc-isp.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/media/platform/exynos4-is/fimc-isp.c
+++ b/drivers/media/platform/exynos4-is/fimc-isp.c
@@ -366,16 +366,16 @@ static int fimc_isp_subdev_s_power(struc
 static int fimc_isp_subdev_open(struct v4l2_subdev *sd,
 				struct v4l2_subdev_fh *fh)
 {
-	struct v4l2_mbus_framefmt fmt;
 	struct v4l2_mbus_framefmt *format;
+	struct v4l2_mbus_framefmt fmt = {
+		.colorspace = V4L2_COLORSPACE_SRGB,
+		.code = fimc_isp_formats[0].mbus_code,
+		.width = DEFAULT_PREVIEW_STILL_WIDTH + FIMC_ISP_CAC_MARGIN_WIDTH,
+		.height = DEFAULT_PREVIEW_STILL_HEIGHT + FIMC_ISP_CAC_MARGIN_HEIGHT,
+		.field = V4L2_FIELD_NONE,
+	};
 
 	format = v4l2_subdev_get_try_format(fh, FIMC_ISP_SD_PAD_SINK);
-
-	fmt.colorspace = V4L2_COLORSPACE_SRGB;
-	fmt.code = fimc_isp_formats[0].mbus_code;
-	fmt.width = DEFAULT_PREVIEW_STILL_WIDTH + FIMC_ISP_CAC_MARGIN_WIDTH;
-	fmt.height = DEFAULT_PREVIEW_STILL_HEIGHT + FIMC_ISP_CAC_MARGIN_HEIGHT;
-	fmt.field = V4L2_FIELD_NONE;
 	*format = fmt;
 
 	format = v4l2_subdev_get_try_format(fh, FIMC_ISP_SD_PAD_SRC_FIFO);