[Intel-gfx] [PATCH i-g-t 2/3] lib/drm_fdinfo: Ensure buffer is null terminated

[Petri Latvala]

On Fri, May 27, 2022 at 11:50:41AM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Ensure buffer is null terminated at the point where the read ended and not
> at the end of the whole buffer. Otherwise string parsing can stray into
> un-initialised memory.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Reviewed-by: Petri Latvala <petri.latvala at intel.com>

> ---
>  lib/igt_drm_fdinfo.c | 8 ++++----
>  lib/igt_drm_fdinfo.h | 4 ++--
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/igt_drm_fdinfo.c b/lib/igt_drm_fdinfo.c
> index b422f67a4ace..250d9e8917f2 100644
> --- a/lib/igt_drm_fdinfo.c
> +++ b/lib/igt_drm_fdinfo.c
> @@ -44,12 +44,12 @@ static size_t read_fdinfo(char *buf, const size_t sz, int at, const char *name)
>  	if (fd < 0)
>  		return 0;
>  
> -	buf[sz - 1] = 0;
> -	count = read(fd, buf, sz);
> -	buf[sz - 1] = 0;
> +	count = read(fd, buf, sz - 1);
> +	if (count > 0)
> +		buf[count - 1] = 0;
>  	close(fd);
>  
> -	return count;
> +	return count > 0 ? count : 0;
>  }
>  
>  static int parse_engine(char *line, struct drm_client_fdinfo *info,
> diff --git a/lib/igt_drm_fdinfo.h b/lib/igt_drm_fdinfo.h
> index 5db63e28b07e..8759471615bd 100644
> --- a/lib/igt_drm_fdinfo.h
> +++ b/lib/igt_drm_fdinfo.h
> @@ -46,7 +46,7 @@ struct drm_client_fdinfo {
>   * igt_parse_drm_fdinfo: Parses the drm fdinfo file
>   *
>   * @drm_fd: DRM file descriptor
> - * @info: Structure to populate with read data
> + * @info: Structure to populate with read data. Must be zeroed.
>   *
>   * Returns the number of valid drm fdinfo keys found or zero if not all
>   * mandatory keys were present or no engines found.
> @@ -58,7 +58,7 @@ unsigned int igt_parse_drm_fdinfo(int drm_fd, struct drm_client_fdinfo *info);
>   *
>   * @dir: File descriptor pointing to /proc/pid/fdinfo directory
>   * @fd: String representation of the file descriptor number to parse.
> - * @info: Structure to populate with read data
> + * @info: Structure to populate with read data. Must be zeroed.
>   *
>   * Returns the number of valid drm fdinfo keys found or zero if not all
>   * mandatory keys were present or no engines found.
> -- 
> 2.32.0
>