util.h: include missing limits.h

Now:
- we don't open the PID file in main() anymore
- PID file and AF_UNIX socket are opened by pidfile_open() and
  tap_sock_unix_open()
- write_pidfile() becomes pidfile_write()

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Acked-by: Richard W.M. Jones <rjones@redhat.com>

conf.c

@@ -38,6 +38,7 @@
 #include "ip.h"
 #include "passt.h"
 #include "netlink.h"
+#include "tap.h"
 #include "udp.h"
 #include "tcp.h"
 #include "pasta.h"
@@ -1093,7 +1094,7 @@ static void conf_ugid(char *runas, uid_t *uid, gid_t *gid)
 		return;
 
 	/* ...otherwise use nobody:nobody */
-	warn("Don't run as root. Changing to nobody...");
+	warn("Started as root, will change to nobody.");
 	{
 #ifndef GLIBC_NO_STATIC_NSS
 		const struct passwd *pw;
@@ -1113,6 +1114,18 @@ static void conf_ugid(char *runas, uid_t *uid, gid_t *gid)
 	}
 }
 
+/**
+ * conf_open_files() - Open files as requested by configuration
+ * @c:		Execution context
+ */
+static void conf_open_files(struct ctx *c)
+{
+	if (c->mode == MODE_PASST && c->fd_tap == -1)
+		c->fd_tap_listen = tap_sock_unix_open(c->sock_path);
+
+	c->pidfile_fd = pidfile_open(c->pidfile);
+}
+
 /**
  * conf() - Process command-line arguments and set configuration
  * @c:		Execution context
@@ -1443,12 +1456,12 @@ void conf(struct ctx *c, int argc, char **argv)
 
 			break;
 		case 'P':
-			if (*c->pid_file)
+			if (*c->pidfile)
 				die("Multiple --pid options given");
 
-			ret = snprintf(c->pid_file, sizeof(c->pid_file), "%s",
+			ret = snprintf(c->pidfile, sizeof(c->pidfile), "%s",
 				       optarg);
-			if (ret <= 0 || ret >= (int)sizeof(c->pid_file))
+			if (ret <= 0 || ret >= (int)sizeof(c->pidfile))
 				die("Invalid PID file: %s", optarg);
 
 			break;
@@ -1712,6 +1725,8 @@ void conf(struct ctx *c, int argc, char **argv)
 	else if (optind != argc)
 		die("Extra non-option argument: %s", argv[optind]);
 
+	conf_open_files(c);	/* Before any possible setuid() / setgid() */
+
 	isolate_user(uid, gid, !netns_only, userns, c->mode);
 
 	if (c->pasta_conf_ns)

contrib/apparmor/abstractions/pasta

@@ -27,7 +27,7 @@
   @{PROC}/@{pid}/net/udp		r,
   @{PROC}/@{pid}/net/udp6		r,
 
-  @{run}/user/@{uid}/**			rw,	# pasta_open_ns(), main()
+  @{run}/user/@{uid}/**			rw,	# pasta_open_ns()
 
   @{PROC}/[0-9]*/ns/			r,	# pasta_netns_quit_init(),
   @{PROC}/[0-9]*/ns/net			r,	# pasta_wait_for_ns(),

contrib/apparmor/usr.bin.passt

@@ -19,9 +19,12 @@ profile passt /usr/bin/passt{,.avx2} {
   include <abstractions/passt>
 
   # Alternatively: include <abstractions/user-tmp>
-  owner /tmp/**				w,	# tap_sock_unix_init(), pcap(),
-						# write_pidfile(),
+  owner /tmp/**				w,	# tap_sock_unix_open(),
+						# tap_sock_unix_init(), pcap(),
+						# pidfile_open(),
+						# pidfile_write(),
 						# logfile_init()
 
-  owner @{HOME}/**			w,	# pcap(), write_pidfile()
+  owner @{HOME}/**			w,	# pcap(), pidfile_open(),
+						# pidfile_write()
 }

contrib/apparmor/usr.bin.pasta

@@ -19,10 +19,13 @@ profile pasta /usr/bin/pasta{,.avx2} flags=(attach_disconnected) {
   include <abstractions/pasta>
 
   # Alternatively: include <abstractions/user-tmp>
-  /tmp/**				rw,	# tap_sock_unix_init(), pcap(),
-						# write_pidfile(),
+  /tmp/**				rw,	# tap_sock_unix_open(),
+						# tap_sock_unix_init(), pcap(),
+						# pidfile_open(),
+						# pidfile_write(),
 						# logfile_init(),
 						# pasta_open_ns()
 
-  owner @{HOME}/**			w,	# pcap(), write_pidfile()
+  owner @{HOME}/**			w,	# pcap(), pidfile_open(),
+						# pidfile_write()
 }

passt.c

@@ -199,9 +199,9 @@ void exit_handler(int signal)
  */
 int main(int argc, char **argv)
 {
-	int nfds, i, devnull_fd = -1, pidfile_fd = -1;
 	struct epoll_event events[EPOLL_EVENTS];
 	char *log_name, argv0[PATH_MAX], *name;
+	int nfds, i, devnull_fd = -1;
 	struct ctx c = { 0 };
 	struct rlimit limit;
 	struct timespec now;
@@ -211,7 +211,7 @@ int main(int argc, char **argv)
 
 	isolate_initial();
 
-	c.pasta_netns_fd = c.fd_tap = c.fd_tap_listen = -1;
+	c.pasta_netns_fd = c.fd_tap = c.pidfile_fd = -1;
 
 	sigemptyset(&sa.sa_mask);
 	sa.sa_flags = 0;
@@ -299,15 +299,6 @@ int main(int argc, char **argv)
 		}
 	}
 
-	if (*c.pid_file) {
-		if ((pidfile_fd = open(c.pid_file,
-				       O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
-				       S_IRUSR | S_IWUSR)) < 0) {
-			perror("PID file open");
-			exit(EXIT_FAILURE);
-		}
-	}
-
 	if (isolate_prefork(&c))
 		die("Failed to sandbox process, exiting");
 
@@ -315,9 +306,9 @@ int main(int argc, char **argv)
 		__openlog(log_name, 0, LOG_DAEMON);
 
 	if (!c.foreground)
-		__daemon(pidfile_fd, devnull_fd);
+		__daemon(c.pidfile_fd, devnull_fd);
 	else
-		write_pidfile(pidfile_fd, getpid());
+		pidfile_write(c.pidfile_fd, getpid());
 
 	if (pasta_child_pid)
 		kill(pasta_child_pid, SIGUSR1);

passt.h

@@ -184,7 +184,8 @@ struct ip6_ctx {
  * @nofile:		Maximum number of open files (ulimit -n)
  * @sock_path:		Path for UNIX domain socket
  * @pcap:		Path for packet capture file
- * @pid_file:		Path to PID file, empty string if not configured
+ * @pidfile:		Path to PID file, empty string if not configured
+ * @pidfile_fd:		File descriptor for PID file, -1 if none
  * @pasta_netns_fd:	File descriptor for network namespace in pasta mode
  * @no_netns_quit:	In pasta mode, don't exit if fs-bound namespace is gone
  * @netns_base:		Base name for fs-bound namespace, if any, in pasta mode
@@ -234,7 +235,10 @@ struct ctx {
 	int nofile;
 	char sock_path[UNIX_PATH_MAX];
 	char pcap[PATH_MAX];
-	char pid_file[PATH_MAX];
+
+	char pidfile[PATH_MAX];
+	int pidfile_fd;
+
 	int one_off;
 
 	int pasta_netns_fd;

tap.c

@@ -1095,14 +1095,14 @@ restart:
 }
 
 /**
- * tap_sock_unix_init() - Create and bind AF_UNIX socket, listen for connection
- * @c:		Execution context
+ * tap_sock_unix_open() - Create and bind AF_UNIX socket
+ * @sock_path:	Socket path. If empty, set on return (UNIX_SOCK_PATH as prefix)
+ *
+ * Return: socket descriptor on success, won't return on failure
  */
-static void tap_sock_unix_init(struct ctx *c)
+int tap_sock_unix_open(char *sock_path)
 {
 	int fd = socket(AF_UNIX, SOCK_STREAM, 0);
-	union epoll_ref ref = { .type = EPOLL_TYPE_TAP_LISTEN };
-	struct epoll_event ev = { 0 };
 	struct sockaddr_un addr = {
 		.sun_family = AF_UNIX,
 	};
@@ -1111,18 +1111,12 @@ static void tap_sock_unix_init(struct ctx *c)
 	if (fd < 0)
 		die("UNIX socket: %s", strerror(errno));
 
-	/* In passt mode, we don't know the guest's MAC until it sends
-	 * us packets.  Use the broadcast address so our first packets
-	 * will reach it.
-	 */
-	memset(&c->mac_guest, 0xff, sizeof(c->mac_guest));
-
 	for (i = 1; i < UNIX_SOCK_MAX; i++) {
 		char *path = addr.sun_path;
 		int ex, ret;
 
-		if (*c->sock_path)
-			memcpy(path, c->sock_path, UNIX_PATH_MAX);
+		if (*sock_path)
+			memcpy(path, sock_path, UNIX_PATH_MAX);
 		else
 			snprintf(path, UNIX_PATH_MAX - 1, UNIX_SOCK_PATH, i);
 
@@ -1133,7 +1127,7 @@ static void tap_sock_unix_init(struct ctx *c)
 		ret = connect(ex, (const struct sockaddr *)&addr, sizeof(addr));
 		if (!ret || (errno != ENOENT && errno != ECONNREFUSED &&
 			     errno != EACCES)) {
-			if (*c->sock_path)
+			if (*sock_path)
 				die("Socket path %s already in use", path);
 
 			close(ex);
@@ -1143,25 +1137,39 @@ static void tap_sock_unix_init(struct ctx *c)
 
 		unlink(path);
 		if (!bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) ||
-		    *c->sock_path)
+		    *sock_path)
 			break;
 	}
 
 	if (i == UNIX_SOCK_MAX)
 		die("UNIX socket bind: %s", strerror(errno));
 
-	info("UNIX domain socket bound at %s\n", addr.sun_path);
+	info("UNIX domain socket bound at %s", addr.sun_path);
+	if (!*sock_path)
+		memcpy(sock_path, addr.sun_path, UNIX_PATH_MAX);
 
-	listen(fd, 0);
+	return fd;
+}
 
-	ref.fd = c->fd_tap_listen = fd;
+/**
+ * tap_sock_unix_init() - Start listening for connections on AF_UNIX socket
+ * @c:		Execution context
+ */
+static void tap_sock_unix_init(struct ctx *c)
+{
+	union epoll_ref ref = { .type = EPOLL_TYPE_TAP_LISTEN };
+	struct epoll_event ev = { 0 };
+
+	listen(c->fd_tap_listen, 0);
+
+	ref.fd = c->fd_tap_listen;
 	ev.events = EPOLLIN | EPOLLET;
 	ev.data.u64 = ref.u64;
 	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap_listen, &ev);
 
-	info("You can now start qemu (>= 7.2, with commit 13c6be96618c):");
+	info("\nYou can now start qemu (>= 7.2, with commit 13c6be96618c):");
 	info("    kvm ... -device virtio-net-pci,netdev=s -netdev stream,id=s,server=off,addr.type=unix,addr.path=%s",
-	     addr.sun_path);
+	     c->sock_path);
 	info("or qrap, for earlier qemu versions:");
 	info("    ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio");
 }
@@ -1310,8 +1318,13 @@ void tap_sock_init(struct ctx *c)
 	}
 
 	if (c->mode == MODE_PASST) {
-		if (c->fd_tap_listen == -1)
 		tap_sock_unix_init(c);
+
+		/* In passt mode, we don't know the guest's MAC address until it
+		 * sends us packets.  Use the broadcast address so that our
+		 * first packets will reach it.
+		 */
+		memset(&c->mac_guest, 0xff, sizeof(c->mac_guest));
 	} else {
 		tap_sock_tun_init(c);
 	}

tap.h

@@ -68,6 +68,7 @@ void tap_handler_pasta(struct ctx *c, uint32_t events,
 		       const struct timespec *now);
 void tap_handler_passt(struct ctx *c, uint32_t events,
 		       const struct timespec *now);
+int tap_sock_unix_open(char *sock_path);
 void tap_sock_init(struct ctx *c);
 
 #endif /* TAP_H */

util.c

@@ -380,11 +380,11 @@ int open_in_ns(const struct ctx *c, const char *path, int flags)
 }
 
 /**
- * pid_file() - Write PID to file, if requested to do so, and close it
+ * pidfile_write() - Write PID to file, if requested to do so, and close it
  * @fd:		Open PID file descriptor, closed on exit, -1 to skip writing it
  * @pid:	PID value to write
  */
-void write_pidfile(int fd, pid_t pid)
+void pidfile_write(int fd, pid_t pid)
 {
 	char pid_buf[12];
 	int n;
@@ -402,6 +402,28 @@ void write_pidfile(int fd, pid_t pid)
 	close(fd);
 }
 
+/**
+ * pidfile_open() - Open PID file if needed
+ * @path:	Path for PID file, empty string if no PID file is requested
+ *
+ * Return: descriptor for PID file, -1 if path is NULL, won't return on failure
+ */
+int pidfile_open(const char *path)
+{
+	int fd;
+
+	if (!*path)
+		return -1;
+
+	if ((fd = open(path, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
+			     S_IRUSR | S_IWUSR)) < 0) {
+		perror("PID file open");
+		exit(EXIT_FAILURE);
+	}
+
+	return fd;
+}
+
 /**
  * __daemon() - daemon()-like function writing PID file before parent exits
  * @pidfile_fd:	Open PID file descriptor
@@ -419,7 +441,7 @@ int __daemon(int pidfile_fd, int devnull_fd)
 	}
 
 	if (pid) {
-		write_pidfile(pidfile_fd, pid);
+		pidfile_write(pidfile_fd, pid);
 		exit(EXIT_SUCCESS);
 	}
 

util.h

@@ -6,6 +6,7 @@
 #ifndef UTIL_H
 #define UTIL_H
 
+#include <limits.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <stdbool.h>
@@ -156,7 +157,8 @@ char *line_read(char *buf, size_t len, int fd);
 void ns_enter(const struct ctx *c);
 bool ns_is_init(void);
 int open_in_ns(const struct ctx *c, const char *path, int flags);
-void write_pidfile(int fd, pid_t pid);
+int pidfile_open(const char *path);
+void pidfile_write(int fd, pid_t pid);
 int __daemon(int pidfile_fd, int devnull_fd);
 int fls(unsigned long x);
 int write_file(const char *path, const char *buf);