pkg_install: Switch to posix_spawn() on newer macOS.

vfork() no longer works on Monterey and causes serious intermittent issues
when upgrading pkg_install.  Forking the INSTALL and DEINSTALL scripts can
sometimes fail, due to the underlying pkg_add/pkg_delete binaries having
been changed or removed, leaving the system broken with no package tools.

The manual page suggests using posix_spawn() instead and that appears to
work correctly.  The code has been laid out so that it's easy enough to
switch other platforms to posix_spawn() too if required, or for improved
performance, and has been verified to work successfully on SmartOS.

Bump pkg_install version to 20211115.

2 files changed, 67 insertions, 4 deletions

diff --git a/pkgtools/pkg_install/files/lib/fexec.c b/pkgtools/pkg_install/files/lib/fexec.c
index 540159863aa..6bf313367de 100644
--- a/pkgtools/pkg_install/files/lib/fexec.c
+++ b/pkgtools/pkg_install/files/lib/fexec.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: fexec.c,v 1.12 2009/08/02 17:56:45 joerg Exp $	*/
+/*	$NetBSD: fexec.c,v 1.13 2021/11/15 12:48:23 jperkin Exp $	*/
 
 /*-
  * Copyright (c) 2003 The NetBSD Foundation, Inc.
@@ -37,6 +37,12 @@
 #if HAVE_SYS_CDEFS_H
 #include <sys/cdefs.h>
 #endif
+#if HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#if HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
 #if HAVE_SYS_WAIT_H
 #include <sys/wait.h>
 #endif
@@ -47,6 +53,9 @@
 #if HAVE_ERRNO_H
 #include <errno.h>
 #endif
+#if HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
 #if HAVE_STDARG_H
 #include <stdarg.h>
 #endif
@@ -59,7 +68,33 @@
 
 #include "lib.h"
 
-__RCSID("$NetBSD: fexec.c,v 1.12 2009/08/02 17:56:45 joerg Exp $");
+/*
+ * Newer macOS releases are not able to correctly handle vfork() when the
+ * underlying file is changed or removed, as is the case when upgrading
+ * pkg_install itself.  The manual pages suggest using posix_spawn()
+ * instead, which seems to work ok.
+ */
+#if defined(__APPLE__) && \
+	((__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__-0) >= 1050)
+#define FEXEC_USE_POSIX_SPAWN	1
+#else
+#define FEXEC_USE_POSIX_SPAWN	0
+#endif
+
+#if FEXEC_USE_POSIX_SPAWN
+#include <spawn.h>
+extern char **environ;
+
+#ifndef O_CLOEXEC
+#define O_CLOEXEC	0
+#endif
+
+#ifndef O_DIRECTORY
+#define O_DIRECTORY	0
+#endif
+#endif
+
+__RCSID("$NetBSD: fexec.c,v 1.13 2021/11/15 12:48:23 jperkin Exp $");
 
 static int	vfcexec(const char *, int, const char *, va_list);
 
@@ -67,6 +102,8 @@ static int	vfcexec(const char *, int, const char *, va_list);
  * fork, then change current working directory to path and
  * execute the command and arguments in the argv array.
  * wait for the command to finish, then return the exit status.
+ *
+ * macOS uses posix_spawn() instead due to reasons explained above.
  */
 int
 pfcexec(const char *path, const char *file, const char **argv)
@@ -74,6 +111,31 @@ pfcexec(const char *path, const char *file, const char **argv)
 	pid_t			child;
 	int			status;
 
+#if FEXEC_USE_POSIX_SPAWN
+	int prevcwd;
+
+	if ((prevcwd = open(".", O_RDONLY|O_CLOEXEC|O_DIRECTORY)) < 0) {
+		warn("open prevcwd failed");
+		return -1;
+	}
+
+	if ((path != NULL) && (chdir(path) < 0)) {
+		warn("chdir %s failed", path);
+		return -1;
+	}
+
+	if (posix_spawn(&child, file, NULL, NULL, (char **)argv, environ) < 0) {
+		warn("posix_spawn failed");
+		return -1;
+	}
+
+	if (fchdir(prevcwd) < 0) {
+		warn("fchdir prevcwd failed");
+		return -1;
+	}
+
+	(void)close(prevcwd);
+#else
 	child = vfork();
 	switch (child) {
 	case 0:
@@ -86,6 +148,7 @@ pfcexec(const char *path, const char *file, const char **argv)
 	case -1:
 		return -1;
 	}
+#endif
 
 	while (waitpid(child, &status, 0) < 0) {
 		if (errno != EINTR)
diff --git a/pkgtools/pkg_install/files/lib/version.h b/pkgtools/pkg_install/files/lib/version.h
index 574922c89db..9bd3ab0a0de 100644
--- a/pkgtools/pkg_install/files/lib/version.h
+++ b/pkgtools/pkg_install/files/lib/version.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: version.h,v 1.188 2021/10/21 13:05:25 jperkin Exp $	*/
+/*	$NetBSD: version.h,v 1.189 2021/11/15 12:48:23 jperkin Exp $	*/
 
 /*
  * Copyright (c) 2001 Thomas Klausner.  All rights reserved.
@@ -27,6 +27,6 @@
 #ifndef _INST_LIB_VERSION_H_
 #define _INST_LIB_VERSION_H_
 
-#define PKGTOOLS_VERSION 20211021
+#define PKGTOOLS_VERSION 20211115
 
 #endif /* _INST_LIB_VERSION_H_ */