Fix GH-9754: SaltStack hangs when running php-fpm 8.1.11

SaltStack uses Python subprocess and redirects stderr to stdout which is
then piped to the returned output. If php-fpm starts in daemonized mode,
it should close stderr. However a fix introduced in GH-8913 keeps stderr
around so it can be later restored. That causes the issue reported in
GH-9754. The solution is to keep stderr around only when php-fpm runs in
foreground as the issue is most likely visible only there. Basically
there is no need to restore stderr when php-fpm is daemonized.

Author: bukka

sapi/fpm/fpm/fpm_conf.c

@@ -1282,7 +1282,7 @@ static int fpm_conf_post_process(int force_daemon) /* {{{ */
 		fpm_evaluate_full_path(&fpm_global_config.error_log, NULL, PHP_LOCALSTATEDIR, 0);
 	}
 
-	if (0 > fpm_stdio_save_original_stderr()) {
+	if (!fpm_global_config.daemonize && 0 > fpm_stdio_save_original_stderr()) {
 		return -1;
 	}
 

sapi/fpm/fpm/fpm_stdio.c

@@ -74,7 +74,9 @@ int fpm_stdio_init_final(void)
 
 int fpm_stdio_save_original_stderr(void)
 {
-	/* php-fpm loses STDERR fd after call of the fpm_stdio_init_final(). Check #8555. */
+	/* STDERR fd gets lost after callingfpm_stdio_init_final() (check GH-8555) so it can be saved.
+	 * It should be used only when PHP-FPM is not daemonized otherwise it might break some
+	 * applications (e.g. GH-9754). */
 	zlog(ZLOG_DEBUG, "saving original STDERR fd: dup()");
 	fd_stderr_original = dup(STDERR_FILENO);
 	if (0 > fd_stderr_original) {
@@ -87,7 +89,7 @@ int fpm_stdio_save_original_stderr(void)
 
 int fpm_stdio_restore_original_stderr(int close_after_restore)
 {
-	/* php-fpm loses STDERR fd after call of the fpm_stdio_init_final(). Check #8555. */
+	/* Restore original STDERR fd if it was previously saved. */
 	if (-1 != fd_stderr_original) {
 		zlog(ZLOG_DEBUG, "restoring original STDERR fd: dup2()");
 		if (0 > dup2(fd_stderr_original, STDERR_FILENO)) {
@@ -98,9 +100,6 @@ int fpm_stdio_restore_original_stderr(int close_after_restore)
 				close(fd_stderr_original);
 			}
 		}
-	} else {
-		zlog(ZLOG_DEBUG, "original STDERR fd is not restored, maybe function is called from a child: dup2()");
-		return -1;
 	}
 
 	return 0;