cairo-xlib: Fix out of bounds array access in format cache

The cairo-xlib backend maintains a mapping form cairo_format_t to xrender
formats. This is done via an array. The size of this array is
CAIRO_FORMAT_RGB16_565 + 1 which evaluates to 5.

However, CAIRO_FORMAT_RGB30 has the numeric value 5, too. Thus, using this value
as an index into the array would actually read the following force_precision
field from cairo_xlib_display_t.

This could be triggered by passing CAIRO_FORMAT_RGB30 to
_cairo_xlib_display_get_xrender_format(). From a quick look, I didn't find any
code which would allow doing this, but neither did I find anything allowing
CAIRO_FORMAT_RGB16_565, so it's better to handle this correctly than assert()ing
for this to never happen.

Signed-off-by: Uli Schlachter <psychon@znc.in>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cairo-xlib-private.h b/src/cairo-xlib-private.h
index 4fd725f..822c85b 100644
--- a/src/cairo-xlib-private.h
+++ b/src/cairo-xlib-private.h
@@ -81,7 +81,7 @@ struct _cairo_xlib_display {
 
     int render_major;
     int render_minor;
-    XRenderPictFormat *cached_xrender_formats[CAIRO_FORMAT_RGB16_565 + 1];
+    XRenderPictFormat *cached_xrender_formats[CAIRO_FORMAT_RGB30 + 1];
 
     int force_precision;