[PATCH weston] backends: don't run off the end of strings

[Bill Spitzak]

That won't run off the end of a zero or one-length string.

If strlen() works then there is a nul byte there. The first test against 
'W' will fail because 0 != 'W', and the second test will not be run.

On 10/23/2014 10:21 AM, Derek Foreman wrote:
> Strings from the config parser can be of length 0, so we should check
> that before checking the string's bytes.
>
> The x11 backend's usage is technically safe since the null terminator
> is present, but I've changed it too in case someone's looking at it as
> a reference for new code.
> ---
>   src/compositor-wayland.c | 2 +-
>   src/compositor-x11.c     | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/compositor-wayland.c b/src/compositor-wayland.c
> index bf71a76..e107002 100644
> --- a/src/compositor-wayland.c
> +++ b/src/compositor-wayland.c
> @@ -2108,7 +2108,7 @@ backend_init(struct wl_display *display, int *argc, char *argv[],
>   		if (name == NULL)
>   			continue;
>
> -		if (name[0] != 'W' || name[1] != 'L') {
> +		if (strlen(name) < 2 || name[0] != 'W' || name[1] != 'L') {
>   			free(name);
>   			continue;
>   		}
> diff --git a/src/compositor-x11.c b/src/compositor-x11.c
> index 1baee29..ae237c8 100644
> --- a/src/compositor-x11.c
> +++ b/src/compositor-x11.c
> @@ -1550,7 +1550,7 @@ x11_compositor_create(struct wl_display *display,
>   		if (strcmp(section_name, "output") != 0)
>   			continue;
>   		weston_config_section_get_string(section, "name", &name, NULL);
> -		if (name == NULL || name[0] != 'X') {
> +		if (name == NULL || strlen(name) < 1 || name[0] != 'X') {
>   			free(name);
>   			continue;
>   		}
>