[PATCH][staging-next] drivers: staging: cedrus: find ctx before dereferencing it ctx

[PATCH][staging-next] drivers: staging: cedrus: find ctx before dereferencing it ctx

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

Currently if count is an invalid value the v4l2_info message will
dereference a null ctx pointer to get the dev information. Fix
this by finding ctx first and then checking for an invalid count,
this way ctxt will be non-null hence avoiding the null pointer
dereference.

Detected by CoverityScan, CID#1475337 ("Explicit null dereferenced")

Fixes: 50e761516f2b ("media: platform: Add Cedrus VPU decoder driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/staging/media/sunxi/cedrus/cedrus.c | 22 ++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
index 82558455384a..699d62dceb6c 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
@@ -108,17 +108,6 @@ static int cedrus_request_validate(struct media_request *req)
 	unsigned int count;
 	unsigned int i;
 
-	count = vb2_request_buffer_cnt(req);
-	if (!count) {
-		v4l2_info(&ctx->dev->v4l2_dev,
-			  "No buffer was provided with the request\n");
-		return -ENOENT;
-	} else if (count > 1) {
-		v4l2_info(&ctx->dev->v4l2_dev,
-			  "More than one buffer was provided with the request\n");
-		return -EINVAL;
-	}
-
 	list_for_each_entry(obj, &req->objects, list) {
 		struct vb2_buffer *vb;
 
@@ -133,6 +122,17 @@ static int cedrus_request_validate(struct media_request *req)
 	if (!ctx)
 		return -ENOENT;
 
+	count = vb2_request_buffer_cnt(req);
+	if (!count) {
+		v4l2_info(&ctx->dev->v4l2_dev,
+			  "No buffer was provided with the request\n");
+		return -ENOENT;
+	} else if (count > 1) {
+		v4l2_info(&ctx->dev->v4l2_dev,
+			  "More than one buffer was provided with the request\n");
+		return -EINVAL;
+	}
+
 	parent_hdl = &ctx->hdl;
 
 	hdl = v4l2_ctrl_request_hdl_find(req, parent_hdl);
-- 
2.19.1

[PATCH][staging-next] drivers: staging: cedrus: find ctx before dereferencing it ctx

[Maxime Ripard]

On Fri, Nov 02, 2018 at 07:01:26PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently if count is an invalid value the v4l2_info message will
> dereference a null ctx pointer to get the dev information. Fix
> this by finding ctx first and then checking for an invalid count,
> this way ctxt will be non-null hence avoiding the null pointer
> dereference.
> 
> Detected by CoverityScan, CID#1475337 ("Explicit null dereferenced")
> 
> Fixes: 50e761516f2b ("media: platform: Add Cedrus VPU decoder driver")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 228 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20181105/bcf2cebe/attachment.sig>

[PATCH][staging-next] drivers: staging: cedrus: find ctx before dereferencing it ctx

[Hans Verkuil]

On 11/02/18 20:01, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently if count is an invalid value the v4l2_info message will
> dereference a null ctx pointer to get the dev information. Fix
> this by finding ctx first and then checking for an invalid count,
> this way ctxt will be non-null hence avoiding the null pointer
> dereference.
> 
> Detected by CoverityScan, CID#1475337 ("Explicit null dereferenced")
> 
> Fixes: 50e761516f2b ("media: platform: Add Cedrus VPU decoder driver")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/staging/media/sunxi/cedrus/cedrus.c | 22 ++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
> index 82558455384a..699d62dceb6c 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> @@ -108,17 +108,6 @@ static int cedrus_request_validate(struct media_request *req)
>  	unsigned int count;
>  	unsigned int i;
>  
> -	count = vb2_request_buffer_cnt(req);
> -	if (!count) {
> -		v4l2_info(&ctx->dev->v4l2_dev,
> -			  "No buffer was provided with the request\n");
> -		return -ENOENT;
> -	} else if (count > 1) {
> -		v4l2_info(&ctx->dev->v4l2_dev,
> -			  "More than one buffer was provided with the request\n");
> -		return -EINVAL;
> -	}
> -
>  	list_for_each_entry(obj, &req->objects, list) {
>  		struct vb2_buffer *vb;
>  
> @@ -133,6 +122,17 @@ static int cedrus_request_validate(struct media_request *req)
>  	if (!ctx)
>  		return -ENOENT;
>  
> +	count = vb2_request_buffer_cnt(req);
> +	if (!count) {
> +		v4l2_info(&ctx->dev->v4l2_dev,
> +			  "No buffer was provided with the request\n");
> +		return -ENOENT;
> +	} else if (count > 1) {
> +		v4l2_info(&ctx->dev->v4l2_dev,
> +			  "More than one buffer was provided with the request\n");
> +		return -EINVAL;
> +	}
> +

Is this right? If there are no buffers in the request, then the list_for_each_entry()
loop won't find a ctx either. This needs to be done differently: for these initial
v4l2_info() statements you can get the cedrus_dev struct from req->mdev since the
media_device is embedded in the cedrus_dev struct. In other words, some
container_of magic is needed here.

Regards,

	Hans

>  	parent_hdl = &ctx->hdl;
>  
>  	hdl = v4l2_ctrl_request_hdl_find(req, parent_hdl);
>