libdaemon: implement daemon_close_stray_fds

Refactor existing code from tools/lvmcmdline.c to
libdaemon/server/daemon-stray.h daemon_close_stray_fds()
used to close stray descriptors above some specified Fd.

This is code parses content of /proc dir to minimize 'blind' closing
of all possible descriptors within rlimits range.

As we have the same code in few other places in it's more 'trivial'
version - these were actually sensitive to high amount of descriptors,
which might be configured on some system.

With this patch we effectively resolve this reported gitlab issue:
https://gitlab.com/lvmteam/lvm2/-/issues/5

TODO: Current placement might not be ideal - however considering
existing code base constrains it's not so simple.
ATM it uses lib/misc/lvm-file.h  for custom_fds declaration
and rest of functinality is included in daemon header file.

libdaemon/server/daemon-server.c

@@ -14,6 +14,7 @@
 
 #include "daemon-server.h"
 #include "daemon-log.h"
+#include "daemon-stray.h"
 #include "libdaemon/client/daemon-io.h"
 
 #include <dlfcn.h>
@@ -326,11 +327,14 @@ static void _remove_lockfile(const char *file)
 static void _daemonise(daemon_state s)
 {
 	int child_status;
-	int fd, ffd;
+	int fd;
 	pid_t pid;
-	struct rlimit rlim;
 	struct timeval tval;
 	sigset_t my_sigset;
+	struct custom_fds custom_fds = {
+		/* Do not close fds preloaded by systemd! */
+		.out = (_systemd_activation) ? SD_FD_SOCKET_SERVER : -1
+	};
 
 	if ((fd = open("/dev/null", O_RDWR)) == -1) {
 		fprintf(stderr, "Unable to open /dev/null.\n");
@@ -392,20 +396,7 @@ static void _daemonise(daemon_state s)
 		exit(3);
 	}
 
-	/* Switch to sysconf(_SC_OPEN_MAX) ?? */
+	daemon_close_stray_fds(s.name, 0, STDERR_FILENO, &custom_fds);
-	if (getrlimit(RLIMIT_NOFILE, &rlim) < 0)
-		ffd = 256; /* just have to guess */
-	else
-		ffd = rlim.rlim_cur;
-
-	for (--ffd; ffd > STDERR_FILENO; ffd--) {
-#ifdef __linux__
-		/* Do not close fds preloaded by systemd! */
-		if (_systemd_activation && ffd == SD_FD_SOCKET_SERVER)
-			continue;
-#endif
-		(void) close(ffd);
-	}
 
 	setsid();
 

libdaemon/server/daemon-stray.h

@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * This file is part of LVM2.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU Lesser General Public License v.2.1.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef _LVM_DAEMON_STRAY_H
+#define _LVM_DAEMON_STRAY_H
+
+/*
+ * needs dm -> #include "device_mapper/all.h"
+ * needs logging -> #include "libdm/misc/dmlib.h"
+ */
+#include "lib/misc/lvm-file.h"
+
+/*
+ * When compiling with valgrind pool support, skip closing descriptors
+ * as there is couple more of them being held by valgrind itself.
+ */
+#ifndef VALGRIND_POOL
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/syscall.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <limits.h>
+
+#ifdef HAVE_VALGRIND
+#include <valgrind.h>
+#endif
+
+static void _daemon_get_cmdline(pid_t pid, char *cmdline, size_t size)
+{
+	char buf[sizeof(DEFAULT_PROC_DIR) + 32];
+	int fd, n = 0;
+
+	snprintf(buf, sizeof(buf), DEFAULT_PROC_DIR "/%u/cmdline", pid);
+	/* FIXME Use generic read code. */
+	if ((fd = open(buf, O_RDONLY)) >= 0) {
+		if ((n = read(fd, cmdline, size - 1)) < 0) {
+			//perror("read", buf);
+			n = 0;
+		}
+		(void) close(fd);
+	}
+	cmdline[n] = '\0';
+}
+
+static void _daemon_get_filename(int fd, char *filename, size_t size)
+{
+	char buf[sizeof(DEFAULT_PROC_DIR) + 32];
+	ssize_t lsize;
+
+	snprintf(buf, sizeof(buf), DEFAULT_PROC_DIR "/self/fd/%u", fd);
+
+	if ((lsize = readlink(buf, filename, sizeof(filename) - 1)) == -1)
+		filename[0] = '\0';
+	else
+		filename[lsize] = '\0';
+}
+
+static void _daemon_close_descriptor(int fd, unsigned suppress_warnings,
+				     const char *command, pid_t ppid,
+				     const char *parent_cmdline)
+{
+	char filename[PATH_MAX];
+	int r;
+
+	/* Ignore bad file descriptors */
+	if (!is_valid_fd(fd))
+		return;
+
+	if (!suppress_warnings)
+		_daemon_get_filename(fd, filename, sizeof(filename));
+
+	r = close(fd);
+	if ((fd <= STDERR_FILENO) || suppress_warnings)
+		return;
+
+	if (!r)
+		fprintf(stderr, "File descriptor %d (%s) leaked on "
+			"%s invocation.", fd, filename, command);
+	else if (errno == EBADF)
+		return;
+	else
+		fprintf(stderr, "Close failed on stray file descriptor "
+			"%d (%s): %s", fd, filename, strerror(errno));
+
+	fprintf(stderr, " Parent PID %d: %s\n", (int)ppid, parent_cmdline);
+}
+
+#endif /* VALGRIND_POOL */
+
+/* Close all stray descriptor except custom fds.
+ * Note: when 'from_fd' is set to -1,  unused 'custom_fds' must use same value!
+ *
+ * command:		print command name with warning message
+ * suppress_warning:	whether to print warning messages
+ * above_fd:		close all descriptors above this descriptor
+ * custom_fds:		preserve descriptors from this set of descriptors
+ */
+static int daemon_close_stray_fds(const char *command, int suppress_warning,
+				  int from_fd, const struct custom_fds *custom_fds)
+{
+#ifndef VALGRIND_POOL
+	struct rlimit rlim;
+	int fd;
+	unsigned suppress_warnings = 0;
+	pid_t ppid = getppid();
+	char parent_cmdline[64];
+	static const char _fd_dir[] = DEFAULT_PROC_DIR "/self/fd";
+	struct dirent *dirent;
+	DIR *d;
+
+#ifdef HAVE_VALGRIND
+	if (RUNNING_ON_VALGRIND)
+		/* Skipping close of descriptors within valgrind execution. */
+		return 1;
+#endif /* HAVE_VALGRIND */
+	_daemon_get_cmdline(ppid, parent_cmdline, sizeof(parent_cmdline));
+
+	if ((d = opendir(_fd_dir))) {
+		/* Discover openned descriptors from /proc/self/fd listing */
+		while ((dirent = readdir(d))) {
+			fd = atoi(dirent->d_name);
+			if ((fd > from_fd) &&
+			    (fd != dirfd(d)) &&
+			    (fd != custom_fds->out) &&
+			    (fd != custom_fds->err) &&
+			    (fd != custom_fds->report))
+				_daemon_close_descriptor(fd, suppress_warnings,
+							 command, ppid, parent_cmdline);
+		}
+
+		(void) closedir(d);
+	} else if (errno == ENOENT) {
+		/* Path does not exist, use the old way */
+		if (getrlimit(RLIMIT_NOFILE, &rlim) < 0)
+			fd = 256; /* just have to guess */
+		else if ((fd = (int)rlim.rlim_cur) > 65536)
+			fd = 65536; /* do not bother with more then 64K fds */
+
+		while (--fd > from_fd) {
+			if ((fd != custom_fds->out) &&
+			    (fd != custom_fds->err) &&
+			    (fd != custom_fds->report))
+				_daemon_close_descriptor(fd, suppress_warnings, command,
+							 ppid, parent_cmdline);
+		}
+	} else
+		return 0; /* broken system */
+#endif /* VALGRIND_POOL */
+	return 1;
+}
+
+#endif

tools/lvmcmdline.c

@@ -21,6 +21,7 @@
 #include "lvm-version.h"
 #include "lib/locking/lvmlockd.h"
 #include "lib/datastruct/str_list.h"
+#include "libdaemon/server/daemon-stray.h"
 
 /* coverity[unnecessary_header] */
 #include "stub.h"
@@ -34,10 +35,6 @@
 #include <locale.h>
 #include <langinfo.h>
 
-#ifdef HAVE_VALGRIND
-#include <valgrind.h>
-#endif
-
 #ifdef HAVE_GETOPTLONG
 #  include <getopt.h>
 #  define GETOPTLONG_FN(a, b, c, d, e) getopt_long((a), (b), (c), (d), (e))
@@ -3502,137 +3499,6 @@ static int _get_custom_fds(struct custom_fds *custom_fds)
 	       _do_get_custom_fd(LVM_REPORT_FD_ENV_VAR_NAME, &custom_fds->report);
 }
 
-static const char *_get_cmdline(pid_t pid)
-{
-	static char _proc_cmdline[32];
-	char buf[256];
-	int fd, n = 0;
-
-	snprintf(buf, sizeof(buf), DEFAULT_PROC_DIR "/%u/cmdline", pid);
-	/* FIXME Use generic read code. */
-	if ((fd = open(buf, O_RDONLY)) >= 0) {
-		if ((n = read(fd, _proc_cmdline, sizeof(_proc_cmdline) - 1)) < 0) {
-			log_sys_error("read", buf);
-			n = 0;
-		}
-		if (close(fd))
-			log_sys_error("close", buf);
-	}
-	_proc_cmdline[n] = '\0';
-
-	return _proc_cmdline;
-}
-
-static const char *_get_filename(int fd)
-{
-	static char filename[PATH_MAX];
-	char buf[32];	/* Assumes short DEFAULT_PROC_DIR */
-	int size;
-
-	snprintf(buf, sizeof(buf), DEFAULT_PROC_DIR "/self/fd/%u", fd);
-
-	if ((size = readlink(buf, filename, sizeof(filename) - 1)) == -1)
-		filename[0] = '\0';
-	else
-		filename[size] = '\0';
-
-	return filename;
-}
-
-static void _close_descriptor(int fd, unsigned suppress_warnings,
-			      const char *command, pid_t ppid,
-			      const char *parent_cmdline)
-{
-	int r;
-	const char *filename;
-
-	/* Ignore bad file descriptors */
-	if (!is_valid_fd(fd))
-		return;
-
-	if (!suppress_warnings)
-		filename = _get_filename(fd);
-
-	r = close(fd);
-	if (suppress_warnings)
-		return;
-
-	if (!r)
-		fprintf(stderr, "File descriptor %d (%s) leaked on "
-			"%s invocation.", fd, filename, command);
-	else if (errno == EBADF)
-		return;
-	else
-		fprintf(stderr, "Close failed on stray file descriptor "
-			"%d (%s): %s", fd, filename, strerror(errno));
-
-	fprintf(stderr, " Parent PID %" PRIpid_t ": %s\n", ppid, parent_cmdline);
-}
-
-static int _close_stray_fds(const char *command, struct custom_fds *custom_fds)
-{
-#ifndef VALGRIND_POOL
-	struct rlimit rlim;
-	int fd;
-	unsigned suppress_warnings = 0;
-	pid_t ppid = getppid();
-	const char *parent_cmdline = _get_cmdline(ppid);
-	static const char _fd_dir[] = DEFAULT_PROC_DIR "/self/fd";
-	struct dirent *dirent;
-	DIR *d;
-
-#ifdef HAVE_VALGRIND
-	if (RUNNING_ON_VALGRIND) {
-		log_debug("Skipping close of descriptors within valgrind execution.");
-		return 1;
-	}
-#endif
-
-	if (getenv("LVM_SUPPRESS_FD_WARNINGS"))
-		suppress_warnings = 1;
-
-	if (!(d = opendir(_fd_dir))) {
-		if (errno != ENOENT) {
-			log_sys_error("opendir", _fd_dir);
-			return 0; /* broken system */
-		}
-
-		/* Path does not exist, use the old way */
-		if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) {
-			log_sys_error("getrlimit", "RLIMIT_NOFILE");
-			return 1;
-		}
-
-		for (fd = 3; fd < (int)rlim.rlim_cur; fd++) {
-			if ((fd != custom_fds->out) &&
-			    (fd != custom_fds->err) &&
-			    (fd != custom_fds->report)) {
-				_close_descriptor(fd, suppress_warnings, command, ppid,
-						  parent_cmdline);
-			}
-		}
-		return 1;
-	}
-
-	while ((dirent = readdir(d))) {
-		fd = atoi(dirent->d_name);
-		if ((fd > 2) &&
-		    (fd != dirfd(d)) &&
-		    (fd != custom_fds->out) &&
-		    (fd != custom_fds->err) &&
-		    (fd != custom_fds->report)) {
-			_close_descriptor(fd, suppress_warnings,
-					  command, ppid, parent_cmdline);
-		}
-	}
-
-	if (closedir(d))
-		log_sys_debug("closedir", _fd_dir);
-#endif
-
-	return 1;
-}
-
 struct cmd_context *init_lvm(unsigned set_connections,
 			     unsigned set_filters,
 			     unsigned threaded)
@@ -3761,7 +3627,8 @@ int lvm2_main(int argc, char **argv)
 	if (!_get_custom_fds(&custom_fds))
 		return EINIT_FAILED;
 
-	if (!_close_stray_fds(base, &custom_fds))
+	if (!daemon_close_stray_fds(base, getenv("LVM_SUPPRESS_FD_WARNINGS") ? 1 : 0,
+				    STDERR_FILENO, &custom_fds))
 		return EINIT_FAILED;
 
 	if (!init_custom_log_streams(&custom_fds))