gnu: vim: Fix CVE-2017-5953.

* gnu/packages/patches/vim-CVE-2017-5953.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/vim.scm (vim)[source]: Use it.

gnu/local.mk

@@ -954,6 +954,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/util-linux-tests.patch			\
   %D%/packages/patches/upower-builddir.patch			\
   %D%/packages/patches/valgrind-enable-arm.patch		\
+  %D%/packages/patches/vim-CVE-2017-5953.patch			\
   %D%/packages/patches/vorbis-tools-CVE-2014-9638+CVE-2014-9639.patch		\
   %D%/packages/patches/vorbis-tools-CVE-2014-9640.patch		\
   %D%/packages/patches/vorbis-tools-CVE-2015-6749.patch		\

gnu/packages/patches/vim-CVE-2017-5953.patch

@@ -0,0 +1,24 @@
+Fix CVE-2017-5953:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5953
+https://groups.google.com/forum/#!topic/vim_dev/t-3RSdEnrHY
+
+Patch adapted from upstream commit, correcting the transcription error
+in the bounds check:
+
+https://github.com/vim/vim/commit/399c297aa93afe2c0a39e2a1b3f972aebba44c9d
+
+diff --git a/src/spellfile.c b/src/spellfile.c
+index c7d87c6..8b1a3a6 100644
+--- a/src/spellfile.c
++++ b/src/spellfile.c
+@@ -1595,6 +1595,9 @@ spell_read_tree(
+     len = get4c(fd);
+     if (len < 0)
+ 	return SP_TRUNCERROR;
++    if (len >= 0x3fffffff)
++	/* Invalid length, multiply with sizeof(int) would overflow. */
++	return SP_FORMERROR;
+     if (len > 0)
+     {
+ 	/* Allocate the byte array. */

gnu/packages/vim.scm

@@ -63,6 +63,7 @@
              (uri (string-append "https://github.com/vim/vim/archive/v"
                                  version ".tar.gz"))
              (file-name (string-append name "-" version ".tar.gz"))
+             (patches (search-patches "vim-CVE-2017-5953.patch"))
              (sha256
               (base32
                "04samk2bakyixbxyc3p0g6ypls45105sikibg0wc6lmak9bqjs85"))))