master 4a108df0eb: Fix check for whether frames fit into gif images

[Lars Ingebrigtsen]

branch: master
commit 4a108df0ebb68e9ea1073d53c14d8f897e43f21c
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Fix check for whether frames fit into gif images
    
    * src/image.c (gif_load): Really check all frames that they fit.
---
 src/image.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/image.c b/src/image.c
index b6edcf96a0..3afb832407 100644
--- a/src/image.c
+++ b/src/image.c
@@ -8937,16 +8937,19 @@ gif_load (struct frame *f, struct image *img)
 
       /* Check that the selected subimages fit.  It's not clear whether
         the GIF spec requires this, but Emacs can crash if they don't fit.  */
-      for (j = 0; j <= idx; ++j)
+      for (j = 0; j < gif->ImageCount; ++j)
        {
          struct SavedImage *subimage = gif->SavedImages + j;
          int subimg_width = subimage->ImageDesc.Width;
          int subimg_height = subimage->ImageDesc.Height;
          int subimg_top = subimage->ImageDesc.Top;
          int subimg_left = subimage->ImageDesc.Left;
-         if (! (subimg_width >= 0 && subimg_height >= 0
-                && 0 <= subimg_top && subimg_top <= height - subimg_height
-                && 0 <= subimg_left && subimg_left <= width - subimg_width))
+         if (subimg_width < 0
+             || subimg_height < 0
+             || subimg_top < 0
+             || subimg_left < 0
+             || subimg_top + subimg_height > height
+             || subimg_left + subimg_width > width)
            {
              image_error ("Subimage does not fit in image");
              goto gif_error;