linux-kernel - [PATCH v2 07/13] media: imx274: initialize format before v4l2 controls

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Date:   Tue, 24 Apr 2018 10:24:12 +0200
From:   Luca Ceresoli <luca@...aceresoli.net>
To:     linux-media@...r.kernel.org
Cc:     Luca Ceresoli <luca@...aceresoli.net>,
        Leon Luo <leonl@...pardimaging.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 07/13] media: imx274: initialize format before v4l2 controls

The current probe function calls v4l2_ctrl_handler_setup() before
initializing the format info. This triggers call paths such as:
imx274_probe -> v4l2_ctrl_handler_setup -> imx274_s_ctrl ->
imx274_set_exposure, where priv->mode_index is accessed before being
assigned.

This is wrong but does not trigger a visible bug because priv is
zero-initialized and 0 is the default value for priv->mode_index. But
this would become a crash in follow-up commits when mode_index is
replaced by a pointer that must always be valid.

Fix the bug before it shows up by initializing struct members early.

Signed-off-by: Luca Ceresoli <luca@...aceresoli.net>

---
Changed v1 -> v2:
 - add "media: " prefix to commit message
---
 drivers/media/i2c/imx274.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/media/i2c/imx274.c b/drivers/media/i2c/imx274.c
index 63fb94e7da37..8a8a11b8d75d 100644
--- a/drivers/media/i2c/imx274.c
+++ b/drivers/media/i2c/imx274.c
@@ -1632,6 +1632,16 @@ static int imx274_probe(struct i2c_client *client,
 
 	mutex_init(&imx274->lock);
 
+	/* initialize format */
+	imx274->mode_index = IMX274_MODE_3840X2160;
+	imx274->format.width = imx274_formats[0].size.width;
+	imx274->format.height = imx274_formats[0].size.height;
+	imx274->format.field = V4L2_FIELD_NONE;
+	imx274->format.code = MEDIA_BUS_FMT_SRGGB10_1X10;
+	imx274->format.colorspace = V4L2_COLORSPACE_SRGB;
+	imx274->frame_interval.numerator = 1;
+	imx274->frame_interval.denominator = IMX274_DEF_FRAME_RATE;
+
 	/* initialize regmap */
 	imx274->regmap = devm_regmap_init_i2c(client, &imx274_regmap_config);
 	if (IS_ERR(imx274->regmap)) {
@@ -1720,16 +1730,6 @@ static int imx274_probe(struct i2c_client *client,
 		goto err_ctrls;
 	}
 
-	/* initialize format */
-	imx274->mode_index = IMX274_MODE_3840X2160;
-	imx274->format.width = imx274_formats[0].size.width;
-	imx274->format.height = imx274_formats[0].size.height;
-	imx274->format.field = V4L2_FIELD_NONE;
-	imx274->format.code = MEDIA_BUS_FMT_SRGGB10_1X10;
-	imx274->format.colorspace = V4L2_COLORSPACE_SRGB;
-	imx274->frame_interval.numerator = 1;
-	imx274->frame_interval.denominator = IMX274_DEF_FRAME_RATE;
-
 	/* load default control values */
 	ret = imx274_load_default(imx274);
 	if (ret) {
-- 
2.7.4