fix race between mount(2) and exit(2) for mount_mfs.

from netbsd (drochner, newfs.c 1.30, mkfs.c 1.29, no copyright changes)
ok tedu@

2 files changed, 69 insertions, 46 deletions

diff --git a/sbin/newfs/mkfs.c b/sbin/newfs/mkfs.c
index 670fb41251a..b290d00fda7 100644
--- a/sbin/newfs/mkfs.c
+++ b/sbin/newfs/mkfs.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mkfs.c,v 1.23 2003/02/19 00:57:14 millert Exp $	*/
+/*	$OpenBSD: mkfs.c,v 1.24 2003/04/16 10:33:16 markus Exp $	*/
 /*	$NetBSD: mkfs.c,v 1.25 1995/06/18 21:35:38 cgd Exp $	*/
 
 /*
@@ -38,13 +38,12 @@
 #if 0
 static char sccsid[] = "@(#)mkfs.c	8.3 (Berkeley) 2/3/94";
 #else
-static char rcsid[] = "$OpenBSD: mkfs.c,v 1.23 2003/02/19 00:57:14 millert Exp $";
+static char rcsid[] = "$OpenBSD: mkfs.c,v 1.24 2003/04/16 10:33:16 markus Exp $";
 #endif
 #endif /* not lint */
 
 #include <sys/param.h>
 #include <sys/time.h>
-#include <sys/wait.h>
 #include <sys/resource.h>
 #include <ufs/ufs/dinode.h>
 #include <ufs/ufs/dir.h>
@@ -54,7 +53,6 @@ static char rcsid[] = "$OpenBSD: mkfs.c,v 1.23 2003/02/19 00:57:14 millert Exp $
 
 #include <string.h>
 #include <stdlib.h>
-#include <signal.h>
 #include <unistd.h>
 
 #ifndef STANDALONE
@@ -159,7 +157,6 @@ mkfs(pp, fsys, fi, fo)
 	int status;
 	time_t utime;
 	quad_t sizepb;
-	void started();
 	int width;
 	char tmpbuf[100];	/* XXX this will break in about 2,500 years */
 
@@ -175,18 +172,6 @@ mkfs(pp, fsys, fi, fo)
 	time(&utime);
 #endif
 	if (mfs) {
-		ppid = getpid();
-		(void) signal(SIGUSR1, started);
-		if ((i = fork())) {
-			if (i == -1) {
-				perror("mfs");
-				exit(10);
-			}
-			if (waitpid(i, &status, 0) != -1 && WIFEXITED(status))
-				exit(WEXITSTATUS(status));
-			exit(11);
-			/* NOTREACHED */
-		}
 		(void)malloc(0);
 		if (fssize * sectorsize > memleft)
 			fssize = (memleft - 16384) / sectorsize;
@@ -701,18 +686,6 @@ next:
 	pp->p_fsize = sblock.fs_fsize;
 	pp->p_frag = sblock.fs_frag;
 	pp->p_cpg = sblock.fs_cpg;
-	/*
-	 * Notify parent process of success.
-	 * Dissociate from session and tty.
-	 */
-	if (mfs) {
-		kill(ppid, SIGUSR1);
-		(void) setsid();
-		(void) close(0);
-		(void) close(1);
-		(void) close(2);
-		(void) chdir("/");
-	}
 }
 
 /*
@@ -1089,16 +1062,6 @@ iput(ip, ino)
 }
 
 /*
- * Notify parent process that the filesystem has created itself successfully.
- */
-void
-started()
-{
-
-	_exit(0);
-}
-
-/*
  * Replace libc function with one suited to our needs.
  */
 static void *
diff --git a/sbin/newfs/newfs.c b/sbin/newfs/newfs.c
index 7ab1d2755aa..12d50e6efd7 100644
--- a/sbin/newfs/newfs.c
+++ b/sbin/newfs/newfs.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: newfs.c,v 1.36 2003/03/13 09:09:26 deraadt Exp $	*/
+/*	$OpenBSD: newfs.c,v 1.37 2003/04/16 10:33:16 markus Exp $	*/
 /*	$NetBSD: newfs.c,v 1.20 1996/05/16 07:13:03 thorpej Exp $	*/
 
 /*
@@ -44,7 +44,7 @@ static char copyright[] =
 #if 0
 static char sccsid[] = "@(#)newfs.c	8.8 (Berkeley) 4/18/94";
 #else
-static char rcsid[] = "$OpenBSD: newfs.c,v 1.36 2003/03/13 09:09:26 deraadt Exp $";
+static char rcsid[] = "$OpenBSD: newfs.c,v 1.37 2003/04/16 10:33:16 markus Exp $";
 #endif
 #endif /* not lint */
 
@@ -57,6 +57,7 @@ static char rcsid[] = "$OpenBSD: newfs.c,v 1.36 2003/03/13 09:09:26 deraadt Exp
 #include <sys/disklabel.h>
 #include <sys/mount.h>
 #include <sys/sysctl.h>
+#include <sys/wait.h>
 
 #include <ufs/ufs/dir.h>
 #include <ufs/ffs/fs.h>
@@ -71,6 +72,7 @@ static char rcsid[] = "$OpenBSD: newfs.c,v 1.36 2003/03/13 09:09:26 deraadt Exp
 #include <string.h>
 #include <syslog.h>
 #include <unistd.h>
+#include <signal.h>
 #include <util.h>
 #include <err.h>
 
@@ -202,7 +204,13 @@ main(argc, argv)
 	struct stat st;
 	struct statfs *mp;
 	int fsi = -1, fso, len, n, maxpartitions;
-	char *cp, *s1, *s2, *special, *opstring, buf[BUFSIZ];
+	char *cp, *s1, *s2, *special, *opstring;
+#ifdef MFS
+	char mountfromname[BUFSIZ];
+	pid_t pid, res;
+	struct statfs sf;
+	int status;
+#endif
 	char *fstype = NULL;
 	char **saveargv = argv;
 	int ffs = 1;
@@ -588,9 +596,61 @@ havelabel:
 #ifdef MFS
 	if (mfs) {
 		struct mfs_args args;
-
-		snprintf(buf, sizeof buf, "mfs:%ld", (long)getpid());
-		args.fspec = buf;
+ 
+ 		switch (pid = fork()) {
+ 		case -1:
+ 			perror("mfs");
+ 			exit(10);
+ 		case 0:
+ 			snprintf(mountfromname, sizeof(mountfromname),
+			    "mfs:%d", getpid());
+ 			break;
+ 		default:
+ 			snprintf(mountfromname, sizeof(mountfromname),
+			    "mfs:%d", pid);
+ 			for (;;) {
+ 				/*
+ 				 * spin until the mount succeeds
+ 				 * or the child exits
+ 				 */
+ 				usleep(1);
+ 
+ 				/*
+ 				 * XXX Here is a race condition: another process
+ 				 * can mount a filesystem which hides our
+ 				 * ramdisk before we see the success.
+ 				 */
+ 				if (statfs(argv[1], &sf) < 0)
+ 					err(88, "statfs %s", argv[1]);
+ 				if (!strcmp(sf.f_mntfromname, mountfromname) &&
+ 				    !strncmp(sf.f_mntonname, argv[1],
+ 					     MNAMELEN) &&
+ 				    !strcmp(sf.f_fstypename, "mfs"))
+ 					exit(0);
+ 
+ 				res = waitpid(pid, &status, WNOHANG);
+ 				if (res == -1)
+ 					err(11, "waitpid");
+ 				if (res != pid)
+ 					continue;
+ 				if (WIFEXITED(status)) {
+ 					if (WEXITSTATUS(status) == 0)
+ 						exit(0);
+ 					errx(1, "%s: mount: %s", argv[1],
+ 					     strerror(WEXITSTATUS(status)));
+ 				} else
+ 					errx(11, "abnormal termination");
+ 			}
+ 			/* NOTREACHED */
+ 		}
+ 
+ 		(void) setsid();
+ 		(void) close(0);
+ 		(void) close(1);
+ 		(void) close(2);
+ 		(void) chdir("/");
+ 
+ 		args.fspec = mountfromname;
 		args.export_info.ex_root = -2;
 		if (mntflags & MNT_RDONLY)
 			args.export_info.ex_flags = MNT_EXRDONLY;
@@ -599,7 +659,7 @@ havelabel:
 		args.base = membase;
 		args.size = fssize * sectorsize;
 		if (mount(MOUNT_MFS, argv[1], mntflags, &args) < 0)
-			fatal("%s: %s", argv[1], strerror(errno));
+			exit(errno); /* parent prints message */
 	}
 #endif
 	exit(0);