Re: [v4l-utils PATCH 1/2] libmediactl: Drop length argument from media_get_entity_by_name()

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

Hi Sakari,

Thank you for the patch.

On Tuesday 24 May 2016 15:48:02 Sakari Ailus wrote:
> Recently it was decided that the API dealing with string operations would
> be better to just receive a nul-terminated string rather than a string the
> length of which is defined. This change was implemented for
> v4l2_subdev_string_to_pixelcode() and v4l2_subdev_string_to_field()
> functions by patch "v4l: libv4l2subdev: Drop length argument from string
> conversion functions" (commit id
> 341f4343e6190a7ceb546f7c74fa67e1cc9ae79f).
> 
> Do the same change for media_get_entity_by_name() in libmediactl. No other
> functions using length argument for strings remain in libmediactl.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  utils/media-ctl/libmediactl.c | 19 +++++++++----------
>  utils/media-ctl/media-ctl.c   |  3 +--
>  utils/media-ctl/mediactl.h    |  3 +--
>  3 files changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/utils/media-ctl/libmediactl.c b/utils/media-ctl/libmediactl.c
> index 89ac11c..78caa7c 100644
> --- a/utils/media-ctl/libmediactl.c
> +++ b/utils/media-ctl/libmediactl.c
> @@ -66,21 +66,14 @@ struct media_pad *media_entity_remote_source(struct
> media_pad *pad) }
> 
>  struct media_entity *media_get_entity_by_name(struct media_device *media,
> -					      const char *name, size_t length)
> +					      const char *name)
>  {
>  	unsigned int i;
> 
> -	/* A match is impossible if the entity name is longer than the maximum
> -	 * size we can get from the kernel.
> -	 */
> -	if (length >= FIELD_SIZEOF(struct media_entity_desc, name))
> -		return NULL;
> -
>  	for (i = 0; i < media->entities_count; ++i) {
>  		struct media_entity *entity = &media->entities[i];
> 
> -		if (strncmp(entity->info.name, name, length) == 0 &&
> -		    entity->info.name[length] == '\0')
> +		if (strcmp(entity->info.name, name) == 0)

While the kernel API guarantees that entity->info.name will be NULL-
terminated, wouldn't it be safer to add a safety check here ?

>  			return entity;
>  	}
> 
> @@ -804,6 +797,8 @@ struct media_pad *media_parse_pad(struct media_device
> *media, for (; isspace(*p); ++p);
> 
>  	if (*p == '"' || *p == '\'') {
> +		char *name;
> +
>  		for (end = (char *)p + 1; *end && *end != '"' && *end != '\''; ++end);
>  		if (*end != '"' && *end != '\'') {
>  			media_dbg(media, "missing matching '\"'\n");
> @@ -811,7 +806,11 @@ struct media_pad *media_parse_pad(struct media_device
> *media, return NULL;
>  		}
> 
> -		entity = media_get_entity_by_name(media, p + 1, end - p - 1);
> +		name = strndup(p + 1, end - p - 1);
> +		if (!name)
> +			return NULL;
> +		entity = media_get_entity_by_name(media, name);
> +		free(name);
>  		if (entity == NULL) {
>  			media_dbg(media, "no such entity \"%.*s\"\n", end - p - 1, p + 1);
>  			*endp = (char *)p + 1;
> diff --git a/utils/media-ctl/media-ctl.c b/utils/media-ctl/media-ctl.c
> index f45ca43..2f049c6 100644
> --- a/utils/media-ctl/media-ctl.c
> +++ b/utils/media-ctl/media-ctl.c
> @@ -559,8 +559,7 @@ int main(int argc, char **argv)
>  	if (media_opts.entity) {
>  		struct media_entity *entity;
> 
> -		entity = media_get_entity_by_name(media, media_opts.entity,
> -						  strlen(media_opts.entity));
> +		entity = media_get_entity_by_name(media, media_opts.entity);
>  		if (entity == NULL) {
>  			printf("Entity '%s' not found\n", media_opts.entity);
>  			goto out;
> diff --git a/utils/media-ctl/mediactl.h b/utils/media-ctl/mediactl.h
> index 77ac182..b5a92f5 100644
> --- a/utils/media-ctl/mediactl.h
> +++ b/utils/media-ctl/mediactl.h
> @@ -245,14 +245,13 @@ static inline unsigned int media_entity_type(struct
> media_entity *entity) * @brief Find an entity by its name.
>   * @param media - media device.
>   * @param name - entity name.
> - * @param length - size of @a name.
>   *
>   * Search for an entity with a name equal to @a name.
>   *
>   * @return A pointer to the entity if found, or NULL otherwise.
>   */
>  struct media_entity *media_get_entity_by_name(struct media_device *media,
> -	const char *name, size_t length);
> +	const char *name);
> 
>  /**
>   * @brief Find an entity by its ID.

-- 
Regards,

Laurent Pinchart