Module Name: src
Committed By: gson
Date: Sat Mar 29 13:50:53 UTC 2014
Modified Files:
src/usr.sbin/nfsd: nfsd.c
Log Message:
When daemonizing, delay the parent exit until the daemon is
ready to provide service. Fixes one of the race conditions
of PR misc/48282.
To generate a diff of this commit:
cvs rdiff -u -r1.61 -r1.62 src/usr.sbin/nfsd/nfsd.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.sbin/nfsd/nfsd.c
diff -u src/usr.sbin/nfsd/nfsd.c:1.61 src/usr.sbin/nfsd/nfsd.c:1.62
--- src/usr.sbin/nfsd/nfsd.c:1.61 Wed Aug 15 00:16:06 2012
+++ src/usr.sbin/nfsd/nfsd.c Sat Mar 29 13:50:53 2014
@@ -1,4 +1,4 @@
-/* $NetBSD: nfsd.c,v 1.61 2012/08/15 00:16:06 joerg Exp $ */
+/* $NetBSD: nfsd.c,v 1.62 2014/03/29 13:50:53 gson Exp $ */
/*
* Copyright (c) 1989, 1993, 1994
@@ -42,7 +42,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 19
#if 0
static char sccsid[] = "@(#)nfsd.c 8.9 (Berkeley) 3/29/95";
#else
-__RCSID("$NetBSD: nfsd.c,v 1.61 2012/08/15 00:16:06 joerg Exp $");
+__RCSID("$NetBSD: nfsd.c,v 1.62 2014/03/29 13:50:53 gson Exp $");
#endif
#endif /* not lint */
@@ -69,6 +69,7 @@ __RCSID("$NetBSD: nfsd.c,v 1.61 2012/08/
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
+#include <paths.h>
#include <pwd.h>
#include <pthread.h>
#include <signal.h>
@@ -249,6 +250,124 @@ out:
}
/*
+ * The functions daemon2_fork() and daemon2_detach() below provide
+ * functionality similar to daemon(3) but split into two phases.
+ * daemon2_fork() is called early, before creating resources that
+ * cannot be inherited across a fork, such as threads or kqueues.
+ * When the daemon is ready to provide service, daemon2_detach()
+ * is called to complete the daemonization and signal the parent
+ * process to exit.
+ *
+ * These functions could potentially be moved to a library and
+ * shared by other daemons.
+ *
+ * The return value from daemon2_fork() is a file descriptor to
+ * be passed as the first argument to daemon2_detach().
+ */
+
+static int
+daemon2_fork(void)
+{
+ int i;
+ int fd;
+ int r;
+ pid_t pid;
+ int detach_msg_pipe[2];
+
+ /*
+ * Set up a pipe for singalling the parent, making sure the
+ * write end does not get allocated one of the file
+ * descriptors that may be closed in daemon2_detach(). The
+ * read end does not need such protection.
+ */
+ for (i = 0; i < 3; i++) {
+ r = pipe2(detach_msg_pipe, O_CLOEXEC|O_NOSIGPIPE);
+ if (r < 0)
+ return -1;
+ if (detach_msg_pipe[1] <= STDERR_FILENO &&
+ (fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
+ (void)dup2(fd, detach_msg_pipe[0]);
+ (void)dup2(fd, detach_msg_pipe[1]);
+ if (fd > STDERR_FILENO)
+ (void)close(fd);
+ continue;
+ }
+ break;
+ }
+
+ pid = fork();
+ switch (pid) {
+ case -1:
+ return -1;
+ case 0:
+ /* child */
+ (void)close(detach_msg_pipe[0]);
+ return detach_msg_pipe[1];
+ default:
+ break;
+ }
+
+ /* Parent */
+ (void)close(detach_msg_pipe[1]);
+
+ for (;;) {
+ ssize_t nread;
+ char dummy;
+ nread = read(detach_msg_pipe[0], &dummy, 1);
+ if (nread < 0) {
+ if (errno == EINTR)
+ continue;
+ _exit(1);
+ } else if (nread == 0) {
+ _exit(1);
+ } else { /* nread > 0 */
+ _exit(0);
+ }
+ }
+}
+
+static int
+daemon2_detach(int parentfd, int nochdir, int noclose)
+{
+ int fd;
+
+ if (setsid() == -1)
+ return -1;
+
+ if (!nochdir)
+ (void)chdir("/");
+
+ if (!noclose && (fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
+ (void)dup2(fd, STDIN_FILENO);
+ (void)dup2(fd, STDOUT_FILENO);
+ (void)dup2(fd, STDERR_FILENO);
+ if (fd > STDERR_FILENO)
+ (void)close(fd);
+ }
+
+ while (1) {
+ ssize_t r = write(parentfd, "", 1);
+ if (r < 0) {
+ if (errno == EINTR)
+ continue;
+ else if (errno == EPIPE)
+ break;
+ else
+ return -1;
+ } else if (r == 0) {
+ /* Should not happen */
+ return -1;
+ } else {
+ break;
+ }
+ }
+
+ (void)close(parentfd);
+
+ return 0;
+}
+
+/*
* Nfs server daemon mostly just a user context for nfssvc()
*
* 1 - do file descriptor and signal cleanup
@@ -279,6 +398,7 @@ main(int argc, char *argv[])
int tcpflag, udpflag;
int ip6flag, ip4flag;
int s, compat;
+ int parent_fd = -1;
#define DEFNFSDCNT 4
nfsdcnt = DEFNFSDCNT;
@@ -348,11 +468,7 @@ main(int argc, char *argv[])
}
if (debug == 0) {
- daemon(0, 0);
- (void)signal(SIGHUP, SIG_IGN);
- (void)signal(SIGINT, SIG_IGN);
- (void)signal(SIGQUIT, SIG_IGN);
- (void)signal(SIGSYS, nonfs);
+ parent_fd = daemon2_fork();
}
openlog("nfsd", LOG_PID, LOG_DAEMON);
@@ -401,6 +517,14 @@ main(int argc, char *argv[])
pthread_setname_np(pthread_self(), "master", NULL);
+ if (debug == 0) {
+ daemon2_detach(parent_fd, 0, 0);
+ (void)signal(SIGHUP, SIG_IGN);
+ (void)signal(SIGINT, SIG_IGN);
+ (void)signal(SIGQUIT, SIG_IGN);
+ (void)signal(SIGSYS, nonfs);
+ }
+
/*
* Loop forever accepting connections and passing the sockets
* into the kernel for the mounts.
