commit e7aa5e101dedd9f636fda06137c992fff8b02ce4
Author: Keith Packard <keithp@keithp.com>
Date:   Fri May 21 09:01:43 2010 -0700

    Don't let alpha maps recurse in fb. Bug 23581.
    
    Recursive alpha maps (where one picture's alpha map is set to a
    picture with an external alpha map) would be all fine and dandy,
    except for the case where the client constructs a loop. Detecting this
    case when setting the alpha map values would be difficult as any time
    an alpha map is set, the server would have to check for the looping
    case.
    
    Instead, a far simpler fix is to simply disallow recursive alpha maps
    in the rendering code, the Render spec is ambiguous in this area and
    allows us to to ignore the recursive case.
    
    Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/fb/fbpict.c b/fb/fbpict.c
index 896d33e..18a5204 100644
--- a/fb/fbpict.c
+++ b/fb/fbpict.c
@@ -332,8 +332,11 @@ create_bits_picture (PicturePtr pict,
     return image;
 }
 
+static pixman_image_t *
+image_from_pict_internal (PicturePtr pict, Bool has_clip, int *xoff, int *yoff, Bool is_alpha_map);
+
 static void
-set_image_properties (pixman_image_t *image, PicturePtr pict, Bool has_clip, int *xoff, int *yoff)
+set_image_properties (pixman_image_t *image, PicturePtr pict, Bool has_clip, int *xoff, int *yoff, Bool is_alpha_map)
 {
     pixman_repeat_t repeat;
     pixman_filter_t filter;
@@ -382,10 +385,13 @@ set_image_properties (pixman_image_t *image, PicturePtr pict, Bool has_clip, int
     
     pixman_image_set_repeat (image, repeat);
     
-    if (pict->alphaMap)
+    /* Fetch alpha map unless 'pict' is being used
+     * as the alpha map for this operation
+     */
+    if (pict->alphaMap && !is_alpha_map)
     {
 	int alpha_xoff, alpha_yoff;
-	pixman_image_t *alpha_map = image_from_pict (pict->alphaMap, FALSE, &alpha_xoff, &alpha_yoff);
+	pixman_image_t *alpha_map = image_from_pict_internal (pict->alphaMap, FALSE, &alpha_xoff, &alpha_yoff, TRUE);
 	
 	pixman_image_set_alpha_map (
 	    image, alpha_map, pict->alphaOrigin.x, pict->alphaOrigin.y);
@@ -417,8 +423,8 @@ set_image_properties (pixman_image_t *image, PicturePtr pict, Bool has_clip, int
     pixman_image_set_source_clipping (image, TRUE);
 }
 
-pixman_image_t *
-image_from_pict (PicturePtr pict, Bool has_clip, int *xoff, int *yoff)
+static pixman_image_t *
+image_from_pict_internal (PicturePtr pict, Bool has_clip, int *xoff, int *yoff, Bool is_alpha_map)
 {
     pixman_image_t *image = NULL;
 
@@ -452,11 +458,17 @@ image_from_pict (PicturePtr pict, Bool has_clip, int *xoff, int *yoff)
     }
     
     if (image)
-	set_image_properties (image, pict, has_clip, xoff, yoff);
+	set_image_properties (image, pict, has_clip, xoff, yoff, is_alpha_map);
     
     return image;
 }
 
+pixman_image_t *
+image_from_pict (PicturePtr pict, Bool has_clip, int *xoff, int *yoff)
+{
+    return image_from_pict_internal (pict, has_clip, xoff, yoff, FALSE);
+}
+
 void
 free_pixman_pict (PicturePtr pict, pixman_image_t *image)
 {