Fix handling of pts(4) device names in comsat(8). Also catch fork() errors.

Pseudo-terminals allocated with posix_openpt(2) will have more slashes
in their path names than comsat(8) allows, so allow slashes when the
character device name starts with "pts/".

This patch is loosely based on NetBSD's changes, revision 1.33. Because
it also included the changes to fork(), I imported them here as well.
Maybe we could import even more fixes from the other BSD's?

Original commit message from the NetBSD folks:

	PR/30170: Markus W Kilbinger: src/libexec/comsat complains
	about: '/' in "/dev/pts/1"

Reported by:	Robert Huff <roberthuff rcn com>

1 files changed, 17 insertions, 6 deletions

diff --git a/libexec/comsat/comsat.c b/libexec/comsat/comsat.c
index ed14b1a2d2bc..fd7cc8d4dc36 100644
--- a/libexec/comsat/comsat.c
+++ b/libexec/comsat/comsat.c
@@ -203,21 +203,32 @@ notify(struct utmp *utp, char file[], off_t offset, int folder)
 	struct stat stb;
 	struct termios tio;
 	char tty[20], name[sizeof(utmp[0].ut_name) + 1];
+	const char *cr = utp->ut_line;
 
-	(void)snprintf(tty, sizeof(tty), "%s%.*s",
-	    _PATH_DEV, (int)sizeof(utp->ut_line), utp->ut_line);
-	if (strchr(tty + sizeof(_PATH_DEV) - 1, '/')) {
+	if (strncmp(cr, "pts/", 4) == 0)
+		cr += 4;
+	if (strchr(cr, '/')) {
 		/* A slash is an attempt to break security... */
-		syslog(LOG_AUTH | LOG_NOTICE, "'/' in \"%s\"", tty);
+		syslog(LOG_AUTH | LOG_NOTICE, "Unexpected `/' in `%s'",
+		    utp->ut_line);
 		return;
 	}
-	if (stat(tty, &stb) || !(stb.st_mode & (S_IXUSR | S_IXGRP))) {
+	(void)snprintf(tty, sizeof(tty), "%s%.*s",
+	    _PATH_DEV, (int)sizeof(utp->ut_line), utp->ut_line);
+	if (stat(tty, &stb) == -1 || !(stb.st_mode & (S_IXUSR | S_IXGRP))) {
 		dsyslog(LOG_DEBUG, "%s: wrong mode on %s", utp->ut_name, tty);
 		return;
 	}
 	dsyslog(LOG_DEBUG, "notify %s on %s\n", utp->ut_name, tty);
-	if (fork())
+	switch (fork()) {
+	case -1:
+		syslog(LOG_NOTICE, "fork failed (%m)");
 		return;
+	case 0:
+		break;
+	default:
+		return;
+	}
 	(void)signal(SIGALRM, SIG_DFL);
 	(void)alarm((u_int)30);
 	if ((tp = fopen(tty, "w")) == NULL) {