gnu: ghostscript: Add fix for CVE-2015-3228.

* gnu/packages/patches/ghostscript-CVE-2015-3228.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/ghostscript.scm (ghostscript)[source]: Add patch.

gnu/packages/patches/ghostscript-CVE-2015-3228.patch

@@ -0,0 +1,32 @@
+The file names in the upstream patch below were modified to apply to GNU
+ghostscript.
+
+From 0c0b0859ae1aba64861599f0e7f74f143f305932 Mon Sep 17 00:00:00 2001
+From: Chris Liddell <chris.liddell@artifex.com>
+Date: Tue, 7 Jul 2015 16:57:41 +0100
+Subject: [PATCH] Bug 696041: sanity check for memory allocation.
+
+In gs_heap_alloc_bytes(), add a sanity check to ensure we don't overflow the
+variable holding the actual number of bytes we allocate.
+
+No cluster differences
+---
+ gs/base/gsmalloc.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/base/gsmalloc.c b/base/gsmalloc.c
+index 624552d..cad79c2 100644
+--- a/base/gsmalloc.c
++++ b/base/gsmalloc.c
+@@ -178,7 +178,7 @@ gs_heap_alloc_bytes(gs_memory_t * mem, uint size, client_name_t cname)
+     } else {
+         uint added = size + sizeof(gs_malloc_block_t);
+ 
+-        if (mmem->limit - added < mmem->used)
++        if (added <= size || mmem->limit - added < mmem->used)
+             set_msg("exceeded limit");
+         else if ((ptr = (byte *) Memento_label(malloc(added), cname)) == 0)
+             set_msg("failed");
+-- 
+2.4.6
+