Fix CVE-2018-1000097:

https://security-tracker.debian.org/tracker/CVE-2018-1000097
https://nvd.nist.gov/vuln/detail/CVE-2018-1000097

Patch taken from upstream bug report:
https://lists.gnu.org/archive/html/bug-gnu-utils/2018-02/msg00005.html

diff --git a/src/unshar.c b/src/unshar.c
index 80bc3a9..0fc3773 100644
--- a/src/unshar.c
+++ b/src/unshar.c
@@ -240,7 +240,7 @@ find_archive (char const * name, FILE * file, off_t start)
       off_t position = ftello (file);
 
       /* Read next line, fail if no more and no previous process.  */
-      if (!fgets (rw_buffer, BUFSIZ, file))
+      if (!fgets (rw_buffer, rw_base_size, file))
 	{
 	  if (!start)
 	    error (0, 0, _("Found no shell commands in %s"), name);
 value='koszko' selected='selected'>koszko</option>
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<div class='path'>path: <a href='/guix/log/?id=5e3175f743b079eac55b3e33c512538acb2d658d'>root</a>/<a href='/guix/log/gnu?id=5e3175f743b079eac55b3e33c512538acb2d658d'>gnu</a>/<a href='/guix/log/gnu/services?id=5e3175f743b079eac55b3e33c512538acb2d658d'>services</a>/<a href='/guix/log/gnu/services/nfs.scm?id=5e3175f743b079eac55b3e33c512538acb2d658d'>nfs.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/nfs.scm?id=5e3175f743b079eac55b3e33c512538acb2d658d&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-01-19 17:28:31 +0100'>2018-01-19</span></td><td><a href='/guix/commit/gnu/services/nfs.scm?id=162a13740041f907f0ce5c2aa05b52b162b4e81a'>gnu: Consistently Write ‘file system(s)’.</a><span class='msg-avail'>...<span class='msg-tooltip'>It is the GNU way.

* doc/guix.texi (Build Systems, DNS Services): Write ‘file system(s)’.
* gnu/build/vm.scm (create-ext-file-system, create-fat-file-system):
Likewise.
* gnu/packages/backup.scm (dirvish, rsnapshot)[description]: Likewise.
* gnu/packages/check.scm (python-testpath)[description]: Likewise.
* gnu/packages/disk.scm (pydf)[description]: Likewise.
* gnu/packages/file-systems.scm (disorderfs)[synopsis, description]: Likewise.
(glusterfs)[description]: Likewise.
* gnu/packages/haskell.scm (ghc-directory, ghc-system-fileio-bootstrap)
(ghc-system-fileio)[synopsis]: Likewise.
(ghc-fsnotify)[description]: Likewise.
* gnu/packages/linux.scm (proot)[description]: Likewise.
(jmtpfs)[synopsis, description]: Likewise.
* gnu/packages/mate.scm (caja, caja-extensions)[description]: Likewise.
* gnu/packages/storage.scm (ceph)[description]: Likewise.
* gnu/packages/sync.scm (lsyncd)[description]: Likewise.
* gnu/packages/syncthing.scm (syncthing)[synopsis]: Likewise.
(go-github-com-zillode-notify)[description]: Likewise.
* gnu/services/nfs.scm (pipefs-service-type): Likewise.
* guix/scripts/system.scm (perform-action): Likewise.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2016-10-12 19:26:10 +0200'>2016-10-12</span></td><td><a href='/guix/commit/gnu/services/nfs.scm?id=eb419bc9fe46358f750c5f0aed87a9b98a93609e'>gnu: Add NFS related services.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/nfs.scm (pipefs-service-type): New variable,
(gss-service-type): New variable, (idmap-service-type) New variable.

* doc/guix.texi (Network File System): New node.
</span></span></td><td>John Darrington</td></tr>
<tr><td><span title='2016-10-01 09:26:07 +0200'>2016-10-01</span></td><td><a href='/guix/commit/gnu/services/nfs.scm?id=43f7af428e139f64b9ec229eb74918e328a63a5a'>gnu: rpcbind-configuration: Rename pkg to nfs-utils</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/nfs.scm (&lt;rpcbind-configuration&gt;): "pkg" --&gt; "nfs-utils"
</span></span></td><td>John Darrington</td></tr>
<tr><td><span title='2016-09-07 20:26:11 +0200'>2016-09-07</span></td><td><a href='/guix/commit/gnu/services/nfs.scm?id=d6a07ee6751cdd414d702194dbeb0fd71f0781c9'>gnu: Add rpc-daemon service</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/nfs.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
</span></span></td><td>John Darrington</td></tr>