gnu: imagemagick: Fix CVE-2020-27829.

* gnu/packages/patches/imagemagick-CVE-2020-27829.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/imagemagick.scm (source): Add patch.

gnu/local.mk

@@ -1220,6 +1220,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/id3lib-UTF16-writing-bug.patch			\
   %D%/packages/patches/idris-disable-test.patch			\
   %D%/packages/patches/ilmbase-fix-tests.patch			\
+  %D%/packages/patches/imagemagick-CVE-2020-27829.patch		\
   %D%/packages/patches/inetutils-hurd.patch			\
   %D%/packages/patches/inkscape-poppler-0.76.patch		\
   %D%/packages/patches/intel-xed-fix-nondeterminism.patch	\

gnu/packages/imagemagick.scm

@@ -155,7 +155,9 @@ text, lines, polygons, ellipses and Bézier curves.")
                                   version ".tar.xz"))
               (sha256
                (base32
-                "1pkwij76yz7vd5grl6520pgpa912qb6kh34qamx4zfndwcx6cf6b"))))))
+                "1pkwij76yz7vd5grl6520pgpa912qb6kh34qamx4zfndwcx6cf6b"))
+              (patches
+               (search-patches "imagemagick-CVE-2020-27829.patch"))))))
 
 (define-public perl-image-magick
   (package

gnu/packages/patches/imagemagick-CVE-2020-27829.patch

@@ -0,0 +1,27 @@
+We omit the ChangeLog changes below, since they do not apply cleanly.
+
+
+From 6ee5059cd3ac8d82714a1ab1321399b88539abf0 Mon Sep 17 00:00:00 2001
+From: Cristy <urban-warrior@imagemagick.org>
+Date: Mon, 30 Nov 2020 16:26:59 +0000
+Subject: [PATCH] possible TIFF related-heap buffer overflow (alert & POC by
+ Hardik Shah)
+
+---
+ ChangeLog     | 6 ++++++
+ coders/tiff.c | 2 +-
+ 2 files changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/coders/tiff.c b/coders/tiff.c
+index e98f927ab..1eecf17ae 100644
+--- a/coders/tiff.c
++++ b/coders/tiff.c
+@@ -1975,7 +1975,7 @@ static Image *ReadTIFFImage(const ImageInfo *image_info,
+         extent+=image->columns*sizeof(uint32);
+ #endif
+         strip_pixels=(unsigned char *) AcquireQuantumMemory(extent,
+-          sizeof(*strip_pixels));
++          2*sizeof(*strip_pixels));
+         if (strip_pixels == (unsigned char *) NULL)
+           ThrowTIFFException(ResourceLimitError,"MemoryAllocationFailed");
+         (void) memset(strip_pixels,0,extent*sizeof(*strip_pixels));