Fix failure to copy setlocale() return value.

nmisch · nmisch · commit f0a264a36234 · 2015-06-20T12:09:29.000-04:00
POSIX permits setlocale() calls to invalidate any previous setlocale() return values, but commit 5f538ad neglected to account for setlocale(LC_CTYPE, NULL) doing so. The effect was to set the LC_CTYPE environment variable to an unintended value. pg_perm_setlocale() sets this variable to assist PL/Perl; without it, Perl would undo PostgreSQL's locale settings. The known-affected configurations are 32-bit, release builds using Visual Studio 2012 or Visual Studio 2013. Visual Studio 2010 is unaffected, as were all buildfarm-attested configurations. In principle, this bug could leave the wrong LC_CTYPE in effect after PL/Perl use, which could in turn facilitate problems like corrupt tsvector datums. No known platform experiences that consequence, because PL/Perl on Windows does not use this environment variable. The bug has been user-visible, as early postmaster failure, on systems with Windows ANSI code page set to CP936 for "Chinese (Simplified, PRC)" and probably on systems using other multibyte code pages. (SetEnvironmentVariable() rejects values containing character data not valid under the Windows ANSI code page.) Back-patch to 9.4, where the faulty commit first appeared. Reported by Didi Hu and 林鹏程. Reviewed by Tom Lane, though this fix strategy was not his first choice.
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
@@ -183,6 +183,12 @@ pg_perm_setlocale(int category, const char *locale)
 	 */
 	if (category == LC_CTYPE)
 	{
+		static char save_lc_ctype[LC_ENV_BUFSIZE];
+
+		/* copy setlocale() return value before callee invokes it again */
+		strlcpy(save_lc_ctype, result, sizeof(save_lc_ctype));
+		result = save_lc_ctype;
+
 #ifdef ENABLE_NLS
 		SetMessageEncoding(pg_bind_textdomain_codeset(textdomain(NULL)));
 #else
