term-utils: avoid error message string length couting errors

Remove various magic numbers with either a string lenght count, or a
symbolic variable that is recognized by gdb.

[kzak@redhat.com: - use snprintf() everywhere,
                  - check snprintf() return code rather than mess up
                    the code with strlens]

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 32 insertions, 34 deletions

diff --git a/term-utils/ttymsg.c b/term-utils/ttymsg.c
index fb2614ffd..18a723f86 100644
--- a/term-utils/ttymsg.c
+++ b/term-utils/ttymsg.c
@@ -58,6 +58,8 @@
 #include "pathnames.h"
 #include "ttymsg.h"
 
+#define ERR_BUFLEN	(MAXNAMLEN + 1024)
+
 /*
  * Display the contents of a uio structure on a terminal.  Used by wall(1),
  * syslogd(8), and talkd(8).  Forks and finishes in child if write would block,
@@ -68,14 +70,17 @@
 char *
 ttymsg(struct iovec *iov, size_t iovcnt, char *line, int tmout) {
 	static char device[MAXNAMLEN];
-	static char errbuf[MAXNAMLEN+1024];
+	static char errbuf[ERR_BUFLEN];
 	size_t cnt, left;
 	ssize_t wret;
 	struct iovec localiov[6];
-	int fd, forked = 0, errsv;
+	int fd, forked = 0;
+	ssize_t	len = 0;
 
-	if (iovcnt > sizeof(localiov) / sizeof(localiov[0]))
-		return (_("internal error: too many iov's"));
+	if (iovcnt > ARRAY_SIZE(localiov)) {
+		snprintf(errbuf, sizeof(errbuf), _("internal error: too many iov's"));
+		return errbuf;
+	}
 
 	/* The old code here rejected the line argument when it contained a '/',
 	   saying: "A slash may be an attempt to break security...".
@@ -84,11 +89,11 @@ ttymsg(struct iovec *iov, size_t iovcnt, char *line, int tmout) {
 	   already. So, this test was worthless, and these days it is
 	   also wrong since people use /dev/pts/xxx. */
 
-	if (strlen(line) + sizeof(_PATH_DEV) + 1 > sizeof(device)) {
-		sprintf(errbuf, _("excessively long line arg"));
-		return (errbuf);
+	len = snprintf(device, sizeof(device), "%s%s", _PATH_DEV, line);
+	if (len < 0 || len + 1 > (ssize_t) sizeof(device)) {
+		snprintf(errbuf, sizeof(errbuf), _("excessively long line arg"));
+		return errbuf;
 	}
-	sprintf(device, "%s%s", _PATH_DEV, line);
 
 	/*
 	 * open will fail on slip lines or exclusive-use lines
@@ -96,12 +101,12 @@ ttymsg(struct iovec *iov, size_t iovcnt, char *line, int tmout) {
 	 */
 	if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
 		if (errno == EBUSY || errno == EACCES)
-			return (NULL);
-		if (strlen(strerror(errno)) > 1000)
-			return (NULL);
-		sprintf(errbuf, "%s: %m", device);
-		errbuf[1024] = 0;
-		return (errbuf);
+			return NULL;
+
+		len = snprintf(errbuf, sizeof(errbuf), "%s: %m", device);
+		if (len < 0 || len + 1 > (ssize_t) sizeof(errbuf))
+			snprintf(errbuf, sizeof(errbuf), _("open failed"));
+		return errbuf;
 	}
 
 	for (cnt = left = 0; cnt < iovcnt; ++cnt)
@@ -139,19 +144,15 @@ ttymsg(struct iovec *iov, size_t iovcnt, char *line, int tmout) {
 			}
 			cpid = fork();
 			if (cpid < 0) {
-				if (strlen(strerror(errno)) > 1000)
-					sprintf(errbuf, _("cannot fork"));
-				else {
-					errsv = errno;
-					sprintf(errbuf,
-						 _("fork: %s"), strerror(errsv));
-				}
+				len = snprintf(errbuf, sizeof(errbuf), _("fork: %m"));
+				if (len < 0 || len + 1 > (ssize_t) sizeof(errbuf))
+					snprintf(errbuf, sizeof(errbuf), _("cannot fork"));
 				close(fd);
-				return (errbuf);
+				return errbuf;
 			}
 			if (cpid) {	/* parent */
 				close(fd);
-				return (NULL);
+				return NULL;
 			}
 			forked++;
 			/* wait at most tmout seconds */
@@ -174,19 +175,16 @@ ttymsg(struct iovec *iov, size_t iovcnt, char *line, int tmout) {
 			warn(_("write failed: %s"), device);
 		if (forked)
 			_exit(EXIT_FAILURE);
-		if (strlen(strerror(errno)) > 1000)
-			sprintf(errbuf, _("%s: BAD ERROR, message is "
-						 "far too long"), device);
-		else {
-			errsv = errno;
-			sprintf(errbuf, "%s: %s", device,
-				       strerror(errsv));
-		}
-		errbuf[1024] = 0;
-		return (errbuf);
+
+		len = snprintf(errbuf, sizeof(errbuf), "%s: %m", device);
+		if (len < 0 || len + 1 > (ssize_t) sizeof(errbuf))
+			snprintf(errbuf, sizeof(errbuf),
+					_("%s: BAD ERROR, message is "
+					  "far too long"), device);
+		return errbuf;
 	}
 
 	if (forked)
 		_exit(EXIT_SUCCESS);
-	return (NULL);
+	return NULL;
 }