From 584c69e77abb537a7345222648a397a9963c01b7 Mon Sep 17 00:00:00 2001
From: "Timur I. Bakeyev" <timur@FreeBSD.org>
Date: Sat, 15 Oct 2022 04:02:43 +0200
Subject: [PATCH 28/28] s3:lib:system - add FreeBSD proc_fd_pattern

Add support for FreeBSD equivalent of /proc/self/fd through a special
fdescfs mount with option "nodup". This filesystem should be mounted
either to the private $PIDDIR/fd/ directory or to /dev/fd in order to
provide security and performance characteristics similar to Linux.

Signed-off-by: Timur I. Bakeyev <timur@FreeBSD.org>
---
 source3/lib/system.c | 108 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 87 insertions(+), 21 deletions(-)

diff --git a/source3/lib/system.c b/source3/lib/system.c
index 00d31692e00..d22ec08361c 100644
--- a/source3/lib/system.c
+++ b/source3/lib/system.c
@@ -1094,39 +1094,105 @@ int sys_get_number_of_cores(void)
 }
 #endif
 
-static struct proc_fd_pattern {
-	const char *pattern;
-	const char *test_path;
-} proc_fd_patterns[] = {
-	/* Linux */
-	{ "/proc/self/fd/%d", "/proc/self/fd/0" },
-	{ NULL, NULL },
+static bool freebsd_fdesc_check(const char *pattern)
+{
+	char fdesc_path[PATH_MAX];
+	int fd, fd2;
+
+	fd = open(lp_pid_directory(), O_DIRECTORY);
+	if (fd == -1) {
+		DBG_ERR("%s: failed to open pid directory: %s\n",
+			lp_pid_directory(), strerror(errno));
+		return false;
+	}
+
+	snprintf(fdesc_path, sizeof(fdesc_path), pattern, fd);
+
+	fd2 = open(fdesc_path, O_DIRECTORY);
+	if (fd2 == -1) {
+		/*
+		 * Setting O_DIRECTORY on open of fdescfs mount
+		 * without `nodup` option will fail with ENOTDIR.
+		 */
+		if (errno == ENOTDIR) {
+			DBG_ERR("%s: fdescfs filesystem is not mounted with "
+				"'nodup' option. This specific mount option is "
+				"required in order to enable race-free handling "
+				"of paths.\n"
+				"See documentation for Samba's New VFS' "
+				"for more details. The `nodup` mount option was "
+				"introduced in FreeBSD 13.\n", fdesc_path);
+			close(fd);
+			return false;
+		}
+		DBG_ERR("%s: failed to open fdescfs path: %s\n",
+			fdesc_path, strerror(errno));
+		close(fd);
+		return false;
+	}
+	close(fd);
+	close(fd2);
+
+	return true;
+}
+
+static char* linux_pattern(char *buf, size_t bufsize)
+{
+	char proc_fd_path[PATH_MAX];
+	const char *pattern = "/proc/self/fd/%lu";
+	struct stat sb;
+
+	snprintf(proc_fd_path, sizeof(proc_fd_path), pattern, 0);
+	if(stat(proc_fd_path, &sb) == 0) {
+		snprintf(buf, bufsize, "%s", pattern);
+		return buf;
+	}
+	return NULL;
+}
+
+static char* freebsd_pattern(char *buf, size_t bufsize) {
+	const char** base;
+	const char* base_dir[] = {
+		lp_pid_directory(), /* This is a preffered location */
+		"/dev",
+		NULL
+	};
+
+	for(base = &base_dir[0]; *base != NULL; base++) {
+		snprintf(buf, bufsize, "%s/fd/%%lu", *base);
+		if(freebsd_fdesc_check(buf)) {
+			return buf;
+		}
+	}
+	return NULL;
+}
+
+static char* (*proc_fd_patterns[])(char *, size_t) = {
+	linux_pattern,
+	freebsd_pattern,
+	NULL
 };
 
-static const char *proc_fd_pattern;
+static char proc_fd_pattern_buf[PATH_MAX];
+static const char *proc_fd_pattern = NULL;
 
 bool sys_have_proc_fds(void)
 {
-	static bool checked;
-	static bool have_proc_fds;
-	struct proc_fd_pattern *p = NULL;
-	struct stat sb;
-	int ret;
+	static bool checked = false;
+	static bool have_proc_fds = false;
+	char* (**pattern_func)(char *, size_t) = NULL;
 
 	if (checked) {
 		return have_proc_fds;
 	}
 
-	for (p = &proc_fd_patterns[0]; p->test_path != NULL; p++) {
-		ret = stat(p->test_path, &sb);
-		if (ret != 0) {
-			continue;
+	for (pattern_func = &proc_fd_patterns[0]; *pattern_func != NULL; pattern_func++) {
+		if((*pattern_func)(proc_fd_pattern_buf, sizeof(proc_fd_pattern_buf)) != NULL) {
+			have_proc_fds = true;
+			proc_fd_pattern = proc_fd_pattern_buf;
+			break;
 		}
-		have_proc_fds = true;
-		proc_fd_pattern = p->pattern;
-		break;
 	}
-
 	checked = true;
 	return have_proc_fds;
 }
-- 
2.37.1