From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 8 Jan 2021 17:16:00 +0000 (-0500)
Subject: Fix ancient bug in parsing of BRE-mode regular expressions.
X-Git-Tag: REL_14_BETA1~996
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=afcc8772edcec687d87b6f762ca6113229af7291;p=postgresql.git

Fix ancient bug in parsing of BRE-mode regular expressions.

brenext(), when parsing a '*' quantifier, forgot to return any "value"
for the token; per the equivalent case in next(), it should return
value 1 to indicate that greedy rather than non-greedy behavior is
wanted.  The result is that the compiled regexp could behave like 'x*?'
rather than the intended 'x*', if we were unlucky enough to have
a zero in v->nextvalue at this point.  That seems to happen with some
reliability if we have '.*' at the beginning of a BRE-mode regexp,
although that depends on the initial contents of a stack-allocated
struct, so it's not guaranteed to fail.

Found by Alexander Lakhin using valgrind testing.  This bug seems
to be aboriginal in Spencer's code, so back-patch all the way.

Discussion: https://postgr.es/m/16814-6c5e3edd2bdf0d50@postgresql.org
---

diff --git a/src/backend/regex/regc_lex.c b/src/backend/regex/regc_lex.c
index 38617b79fd1..ca2bce48312 100644
--- a/src/backend/regex/regc_lex.c
+++ b/src/backend/regex/regc_lex.c
@@ -994,7 +994,7 @@ brenext(struct vars *v,
 		case CHR('*'):
 			if (LASTTYPE(EMPTY) || LASTTYPE('(') || LASTTYPE('^'))
 				RETV(PLAIN, c);
-			RET('*');
+			RETV('*', 1);
 			break;
 		case CHR('['):
 			if (HAVE(6) && *(v->now + 0) == CHR('[') &&
diff --git a/src/test/modules/test_regex/expected/test_regex.out b/src/test/modules/test_regex/expected/test_regex.out
index ed1b0cbdb9b..0dc2265d8b2 100644
--- a/src/test/modules/test_regex/expected/test_regex.out
+++ b/src/test/modules/test_regex/expected/test_regex.out
@@ -614,6 +614,14 @@ ERROR:  invalid regular expression: quantifier operand invalid
 -- expectError	7.15 -		a*+	BADRPT
 select * from test_regex('a*+', '', '-');
 ERROR:  invalid regular expression: quantifier operand invalid
+-- test for ancient brenext() bug; not currently in Tcl
+select * from test_regex('.*b', 'aaabbb', 'b');
+ test_regex 
+------------
+ {0}
+ {aaabbb}
+(2 rows)
+
 -- doing 8 "braces"
 -- expectMatch	8.1  NQ		"a{0,1}"	""	""
 select * from test_regex('a{0,1}', '', 'NQ');
diff --git a/src/test/modules/test_regex/sql/test_regex.sql b/src/test/modules/test_regex/sql/test_regex.sql
index 4676cd1a060..1a2bfa62357 100644
--- a/src/test/modules/test_regex/sql/test_regex.sql
+++ b/src/test/modules/test_regex/sql/test_regex.sql
@@ -214,6 +214,8 @@ select * from test_regex('a?*', '', '-');
 select * from test_regex('a+*', '', '-');
 -- expectError	7.15 -		a*+	BADRPT
 select * from test_regex('a*+', '', '-');
+-- test for ancient brenext() bug; not currently in Tcl
+select * from test_regex('.*b', 'aaabbb', 'b');
 
 -- doing 8 "braces"