Fix <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-9169>.

Taken from this upstream commit, sans ChangeLog updates:
https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=583dd860d5b833037175247230a328f0050dbfe9

diff --git a/posix/regexec.c b/posix/regexec.c
index 91d5a797b8..084b1222d9 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -1293,8 +1293,10 @@ proceed_next_node (const re_match_context_t *mctx, Idx nregs, regmatch_t *regs,
 	      else if (naccepted)
 		{
 		  char *buf = (char *) re_string_get_buffer (&mctx->input);
-		  if (memcmp (buf + regs[subexp_idx].rm_so, buf + *pidx,
-			      naccepted) != 0)
+		  if (mctx->input.valid_len - *pidx < naccepted
+		      || (memcmp (buf + regs[subexp_idx].rm_so, buf + *pidx,
+				  naccepted)
+			  != 0))
 		    return -1;
 		}
 	    }
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<div class='path'>path: <a href='/guix/log/?id=a7d7795f97c2eccc2a1f6527a412d8a9ab4c21d0'>root</a>/<a href='/guix/log/gnu?id=a7d7795f97c2eccc2a1f6527a412d8a9ab4c21d0'>gnu</a>/<a href='/guix/log/gnu/system?id=a7d7795f97c2eccc2a1f6527a412d8a9ab4c21d0'>system</a>/<a href='/guix/log/gnu/system/privilege.scm?id=a7d7795f97c2eccc2a1f6527a412d8a9ab4c21d0'>privilege.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/system/privilege.scm?id=a7d7795f97c2eccc2a1f6527a412d8a9ab4c21d0&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-09-08 02:00:00 +0200'>2024-09-08</span></td><td><a href='/guix/commit/gnu/system/privilege.scm?id=0dd8e4c35109ed8bc2406a0bc13e18823a334937'>privilege: Add file-like-&gt;setuid-program helper.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/privilege.scm (file-like-&gt;setuid-program): New public
procedure.
* gnu/system/setuid.scm: Re-export it for compatibility.
(file-like-&gt;setuid-program): Remove this old version.
* gnu/services/docker.scm (singularity-setuid-programs): Use it (again).
* gnu/services/desktop.scm (enlightenment-privileged-programs): Likewise.

Change-Id: I8e41144438677a15cdadb3063651dbc780715497
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2024-08-11 02:00:00 +0200'>2024-08-11</span></td><td><a href='/guix/commit/gnu/system/privilege.scm?id=71f0676a295841e2cc662eec0d3e9b7e69726035'>privilege: Add POSIX capabilities(7) support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/privilege.scm (&lt;privileged-program&gt;): Add a field
representing the program's POSIX capabilities.
(privileged-program-capabilities): New public procedure.
* doc/guix.texi (Privileged Programs): Document it.
* gnu/build/activation.scm (activate-privileged-programs): Take a LIBCAP
package argument providing setcap(8) to apply said capabilities.
* gnu/services.scm (privileged-program-&gt;activation-gexp): Pass said
package argument where supported.  Include privileged-program-capabilities
in the compatibility hack.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2024-08-11 02:00:00 +0200'>2024-08-11</span></td><td><a href='/guix/commit/gnu/system/privilege.scm?id=39471f2627bd63df0e9af02a46e5dda60e233ffc'>system: Add (gnu system privilege).</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/privilege.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>