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From: Brooks Davis <brooks@FreeBSD.org>
Date: Tue, 2 May 2017 21:20:27 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: svn commit: r317707 - head/lib/libc/regex
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Author: brooks
Date: Tue May  2 21:20:27 2017
New Revision: 317707
URL: https://svnweb.freebsd.org/changeset/base/317707

Log:
  Correct an out-of-bounds read in regcomp when the RE is bad.
  
  When passed the invalid regular expression "a**", the error is
  eventually detected and seterr() is called. It sets p->error
  appropriatly and p->next and p->end to nuls which is a never used char
  nuls[10] which is zeros due to .bss initialization. Unfortunatly,
  p_ere_exp() and p_simp_re() both have fall through cases where they set
  the error, decrement p->next and access it which means a read from what
  ever .bss variable comes before nuls.
  
  Found with regex_test:repet_multi and CHERI bounds checking.
  
  Reviewed by:	ngie, pfg, emaste
  Obtained from:	CheriBSD
  Sponsored by:	DARPA, AFRL
  MFC after:	1 week
  Differential Revision:	https://reviews.freebsd.org/D10541

Modified:
  head/lib/libc/regex/regcomp.c

Modified: head/lib/libc/regex/regcomp.c
==============================================================================
--- head/lib/libc/regex/regcomp.c	Tue May  2 21:09:07 2017	(r317706)
+++ head/lib/libc/regex/regcomp.c	Tue May  2 21:20:27 2017	(r317707)
@@ -444,6 +444,8 @@ p_ere_exp(struct parse *p)
 		(void)REQUIRE(!MORE() || !isdigit((uch)PEEK()), REG_BADRPT);
 		/* FALLTHROUGH */
 	default:
+		if (p->error != 0)
+			return;
 		p->next--;
 		wc = WGETNEXT();
 		ordinary(p, wc);
@@ -651,6 +653,8 @@ p_simp_re(struct parse *p,
 		(void)REQUIRE(starordinary, REG_BADRPT);
 		/* FALLTHROUGH */
 	default:
+		if (p->error != 0)
+			return(0);	/* Definitely not $... */
 		p->next--;
 		wc = WGETNEXT();
 		ordinary(p, wc);