From: Jeff Davis <jdavis@postgresql.org>
Date: Tue, 27 Jan 2026 16:16:07 +0000 (-0800)
Subject: Fix crash introduced by incorrect backport 806555e300.
X-Git-Tag: REL_18_2~38
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8993bf0991d876c878fe3739d6d4e200a1e122f3;p=thirdparty%2Fpostgresql.git

Fix crash introduced by incorrect backport 806555e300.

Commit 7f007e4a04 in master depends on 1476028225, but the latter was
not backported. Therefore 806555e300 (the backport of commit
7f007e4a04) incorrectly used pg_strfold() in a locale where
ctype_is_c.

The fix is to simply have the callers check for ctype_is_c.

Because 7f007e4a04 was only backported to version 18, and because the
commit in master is fine, this fix only exists in version 18.

Reported-by: Александр Кожемякин <a.kozhemyakin@postgrespro.ru>
Discussion: https://postgr.es/m/456f7143-51ea-4342-b4a1-85f0d9b6c79f@postgrespro.ru
---

diff --git a/contrib/ltree/crc32.c b/contrib/ltree/crc32.c
index ce1b0f28e21..1eeda14651e 100644
--- a/contrib/ltree/crc32.c
+++ b/contrib/ltree/crc32.c
@@ -30,20 +30,34 @@ ltree_crc32_sz(const char *buf, int size)
 		locale = pg_newlocale_from_collation(DEFAULT_COLLATION_OID);
 
 	INIT_TRADITIONAL_CRC32(crc);
-	while (size > 0)
+	if (locale->ctype_is_c)
+	{
+		while (size > 0)
+		{
+			char		c = pg_ascii_tolower(*p);
+
+			COMP_TRADITIONAL_CRC32(crc, &c, 1);
+			size--;
+			p++;
+		}
+	}
+	else
 	{
-		char		foldstr[UNICODE_CASEMAP_BUFSZ];
-		int			srclen = pg_mblen(p);
-		size_t		foldlen;
+		while (size > 0)
+		{
+			char		foldstr[UNICODE_CASEMAP_BUFSZ];
+			int			srclen = pg_mblen(p);
+			size_t		foldlen;
 
-		/* fold one codepoint at a time */
-		foldlen = pg_strfold(foldstr, UNICODE_CASEMAP_BUFSZ, p, srclen,
-							 locale);
+			/* fold one codepoint at a time */
+			foldlen = pg_strfold(foldstr, UNICODE_CASEMAP_BUFSZ, p, srclen,
+								 locale);
 
-		COMP_TRADITIONAL_CRC32(crc, foldstr, foldlen);
+			COMP_TRADITIONAL_CRC32(crc, foldstr, foldlen);
 
-		size -= srclen;
-		p += srclen;
+			size -= srclen;
+			p += srclen;
+		}
 	}
 	FIN_TRADITIONAL_CRC32(crc);
 	return (unsigned int) crc;
diff --git a/contrib/ltree/lquery_op.c b/contrib/ltree/lquery_op.c
index 9b1de101213..f4a507a27c7 100644
--- a/contrib/ltree/lquery_op.c
+++ b/contrib/ltree/lquery_op.c
@@ -96,15 +96,32 @@ ltree_prefix_eq_ci(const char *a, size_t a_sz, const char *b, size_t b_sz)
 	static pg_locale_t locale = NULL;
 	size_t		al_sz = a_sz + 1;
 	size_t		al_len;
-	char	   *al = palloc(al_sz);
+	char	   *al;
 	size_t		bl_sz = b_sz + 1;
 	size_t		bl_len;
-	char	   *bl = palloc(bl_sz);
+	char	   *bl;
 	bool		res;
 
 	if (!locale)
 		locale = pg_newlocale_from_collation(DEFAULT_COLLATION_OID);
 
+	if (locale->ctype_is_c)
+	{
+		if (a_sz > b_sz)
+			return false;
+
+		for (int i = 0; i < a_sz; i++)
+		{
+			if (pg_ascii_tolower(a[i]) != pg_ascii_tolower(b[i]))
+				return false;
+		}
+
+		return true;
+	}
+
+	al = palloc(al_sz);
+	bl = palloc(bl_sz);
+
 	/* casefold both a and b */
 
 	al_len = pg_strfold(al, al_sz, a, a_sz, locale);