Re: segfault in cairo-xcb-surface-render.c

On Thu, May 01, 2014 at 01:48:37PM +0200, thorsten wrote:
> Hello all,
> 
> when using a Firefox compiled against cairo 1.12.16 I get a segfault
> when visiting some webpages, eg when scrolling an expose on
> www.immobilienscout24.de.
> 
> debugging the problem with gdb led me to line 3125 of
> cairo-xcb-surface-render.c:
> 
> _cairo_clip_path_destroy (clip->path);
> 
> where on that webpage for reasons I don't know clip->path = NULL
> 
> I changed the line to
> 
> if (clip->path != NULL) _cairo_clip_path_destroy (clip->path);
> 
> which fixes the segfault.
> 
> See patch below:

Hi Thorsten,

The fix seems sane enough, but I am not able to reproduce the bug, using
cairo 1.12.16 and firefox 29 on the URL you provided.  Mind filing a
bugzilla bug on this with a backtrace, to give a reference for the bug?

Bryce
 
>  cat /usr/src/blfs-src/cairo-1.12.16-fix-segfault.patch
> --- cairo-1.12.16/src/cairo-xcb-surface-render.c-orig   2014-05-01
> 13:31:53.386347915 +0200
> +++ cairo-1.12.16/src/cairo-xcb-surface-render.c        2014-05-01
> 13:32:12.099032718 +0200
> @@ -3123,7 +3123,7 @@
>         clip = _cairo_clip_intersect_boxes (clip, boxes);
>         status = _cairo_clip_get_polygon (clip, &polygon,
>                                           &fill_rule, &antialias);
> -       _cairo_clip_path_destroy (clip->path);
> +       if (clip->path != NULL) _cairo_clip_path_destroy (clip->path);
>         clip->path = NULL;
>         if (likely (status == CAIRO_INT_STATUS_SUCCESS)) {
>             cairo_clip_t *saved_clip = extents->clip;
> 
> 
> regards,
> 
> thorsten
> 
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