linux-kernel - [PATCH] staging: atomisp: move null check to earlier point

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Message-Id: <20200729135636.9220-1-cengiz@kernel.wtf>
Date:   Wed, 29 Jul 2020 16:56:37 +0300
From:   Cengiz Can <cengiz@...nel.wtf>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, Cengiz Can <cengiz@...nel.wtf>
Subject: [PATCH] staging: atomisp: move null check to earlier point

`find_gmin_subdev` function that returns a pointer to `struct
gmin_subdev` can return NULL.

In `gmin_v2p8_ctrl` there's a call to this function but the possibility
of a NULL was not checked before its being dereferenced. ie:

```
/* Acquired here --------v */
struct gmin_subdev *gs = find_gmin_subdev(subdev);
int ret;
int value;

/*  v------Dereferenced here */
if (gs->v2p8_gpio >= 0) {
	pr_info("atomisp_gmin_platform: 2.8v power on GPIO %d\n",
		gs->v2p8_gpio);
	ret = gpio_request(gs->v2p8_gpio, "camera_v2p8");
	if (!ret)
		ret = gpio_direction_output(gs->v2p8_gpio, 0);
	if (ret)
		pr_err("V2P8 GPIO initialization failed\n");
}
```

I have moved the NULL check before deref point.

Caught-by: Coverity Static Analyzer CID 1465536
Signed-off-by: Cengiz Can <cengiz@...nel.wtf>
---
 drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
index 0df46a1af5f0..8e9c5016f299 100644
--- a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
+++ b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
@@ -871,6 +871,11 @@ static int gmin_v2p8_ctrl(struct v4l2_subdev *subdev, int on)
 	int ret;
 	int value;
 
+	if (!gs) {
+		pr_err("Unable to find gmin subdevice\n");
+		return -EINVAL;
+	}
+
 	if (gs->v2p8_gpio >= 0) {
 		pr_info("atomisp_gmin_platform: 2.8v power on GPIO %d\n",
 			gs->v2p8_gpio);
@@ -881,7 +886,7 @@ static int gmin_v2p8_ctrl(struct v4l2_subdev *subdev, int on)
 			pr_err("V2P8 GPIO initialization failed\n");
 	}
 
-	if (!gs || gs->v2p8_on == on)
+	if (gs->v2p8_on == on)
 		return 0;
 	gs->v2p8_on = on;
 
-- 
2.27.0