[src/trunk]: src/lib/libc/regex Add some better error handling from FreeBSD, ...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/39cd27ff2cd7
branches:  trunk
changeset: 839135:39cd27ff2cd7
user:      christos <christos%NetBSD.org@localhost>
date:      Thu Feb 07 22:22:31 2019 +0000

description:
Add some better error handling from FreeBSD, although we don't
suffer from the same issue, since we don't decrement p->next, like
FreeBSD does because we don't have multibyte support (yet). We
choose to do this so we can fail faster and more predictably.

Here's the original FreeBSD message:

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

diffstat:

 lib/libc/regex/regcomp.c |  8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diffs (36 lines):

diff -r d5a9a5dfadd3 -r 39cd27ff2cd7 lib/libc/regex/regcomp.c
--- a/lib/libc/regex/regcomp.c  Thu Feb 07 22:13:52 2019 +0000
+++ b/lib/libc/regex/regcomp.c  Thu Feb 07 22:22:31 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: regcomp.c,v 1.37 2019/02/07 22:13:52 christos Exp $    */
+/*     $NetBSD: regcomp.c,v 1.38 2019/02/07 22:22:31 christos Exp $    */
 
 /*-
  * Copyright (c) 1992, 1993, 1994
@@ -76,7 +76,7 @@
 #if 0
 static char sccsid[] = "@(#)regcomp.c  8.5 (Berkeley) 3/20/94";
 #else
-__RCSID("$NetBSD: regcomp.c,v 1.37 2019/02/07 22:13:52 christos Exp $");
+__RCSID("$NetBSD: regcomp.c,v 1.38 2019/02/07 22:22:31 christos Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -474,6 +474,8 @@
                REQUIRE(!MORE() || !isdigit((unsigned char)PEEK()), REG_BADRPT);
                /* FALLTHROUGH */
        default:
+               if (p->error != 0)
+                       return;
                ordinary(p, c);
                break;
        }
@@ -692,6 +694,8 @@
                REQUIRE(starordinary, REG_BADRPT);
                /* FALLTHROUGH */
        default:
+               if (p->error != 0)
+                       return(0);
                ordinary(p, c &~ BACKSL);
                break;
        }