Re: [PATCH] media: uvcvideo: fix a crash in uvc_ctrl_init_ctrl()

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Dan,

Thank you for the patch.

On Tue, Jul 19, 2022 at 04:45:29PM +0300, Dan Carpenter wrote:
> There is a path where "mapping" is NULL when we try to process the
> common mappings so it will crash.
> 
> Fixes: 86f7ef773156 ("media: uvcvideo: Add support for per-device control mapping overrides")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

I've submitted [1] to fix this issue, and [2] to replace all the
error-prone loops in this function.

[1] https://lore.kernel.org/linux-media/20220718121219.16079-1-laurent.pinchart@ideasonboard.com/
[2] https://lore.kernel.org/linux-media/20220718222757.8203-1-laurent.pinchart@ideasonboard.com/T/#u

> ---
> This bug was previously reported by the kbuild bot and fixed in later
> versions of the patchset.  The git log doesn't have a link to
> lore.kernel.org but I suspect an earlier version got merged?
> 
>  drivers/media/usb/uvc/uvc_ctrl.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index e4826a846861..00ea894e79fd 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -2413,9 +2413,9 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
>  {
>  	const struct uvc_control_info *info = uvc_ctrls;
>  	const struct uvc_control_info *iend = info + ARRAY_SIZE(uvc_ctrls);
> -	const struct uvc_control_mapping *mapping = uvc_ctrl_mappings;
> -	const struct uvc_control_mapping *mend =
> -		mapping + ARRAY_SIZE(uvc_ctrl_mappings);
> +	const struct uvc_control_mapping *mapping;
> +	const struct uvc_control_mapping *mend;
> +	unsigned int i;
>  
>  	/*
>  	 * XU controls initialization requires querying the device for control
> @@ -2453,7 +2453,6 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
>  	 */
>  	if (chain->dev->info->mappings) {
>  		bool custom = false;
> -		unsigned int i;
>  
>  		for (i = 0; (mapping = chain->dev->info->mappings[i]); ++i) {
>  			if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
> @@ -2468,7 +2467,8 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
>  	}
>  
>  	/* Process common mappings next. */
> -	for (; mapping < mend; ++mapping) {
> +	for (i = 0; i < ARRAY_SIZE(uvc_ctrl_mappings); i++) {
> +		mapping = &uvc_ctrl_mappings[i];
>  		if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
>  		    ctrl->info.selector == mapping->selector)
>  			__uvc_ctrl_add_mapping(chain, ctrl, mapping);
> -- 
> 2.35.1
> 

-- 
Regards,

Laurent Pinchart