Properly match (ttymaj, ttymin) pairs to tty names in /dev

For the common case where we have pts/ or tty do it straight
away.  Otherwise traverse /dev for a match.  This fixes ps(1) when
it is executed over a serial terminal with tty names like ttyAMA0.

libutil/tty.c

@@ -1,7 +1,13 @@
 /* See LICENSE file for copyright and license details. */
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <dirent.h>
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "../util.h"
 
@@ -12,28 +18,63 @@ devtotty(int dev, int *tty_maj, int *tty_min)
 	*tty_min = (dev & 0xff) | ((dev >> 12) & 0xfff00);
 }
 
-char *
-ttytostr(int tty_maj, int tty_min)
+int
+ttytostr(int tty_maj, int tty_min, char *str, size_t n)
 {
-	const char *pts = "pts/";
-	const char *tty = "tty";
-	char *ttystr;
-	size_t len;
+	struct stat sb;
+	struct dirent *dp;
+	DIR *dirp;
+	char path[PATH_MAX];
 
-	/* Up to 10k ttys */
-	len = strlen(pts) + 4 + 1;
-	ttystr = emalloc(len);
 	switch (tty_maj) {
 	case 136:
-		snprintf(ttystr, len, "%s%d", pts, tty_min);
-		break;
+		snprintf(str, n, "pts/%d", tty_min);
+		return 0;
 	case 4:
-		snprintf(ttystr, len, "%s%d", tty, tty_min);
-		break;
+		snprintf(str, n, "tty%d", tty_min);
+		return 0;
 	default:
-		ttystr[0] = '?';
-		ttystr[1] = '\0';
+		str[0] = '?';
+		str[1] = '\0';
 		break;
 	}
-	return ttystr;
+
+	dirp = opendir("/dev");
+	if (!dirp) {
+		weprintf("opendir /dev:");
+		return -1;
+	}
+
+	while ((dp = readdir(dirp))) {
+		if (!strcmp(dp->d_name, ".") ||
+		    !strcmp(dp->d_name, ".."))
+			continue;
+
+		if (strlcpy(path, "/dev/", sizeof(path)) >= sizeof(path)) {
+			weprintf("path too long\n");
+			return -1;
+		}
+		if (strlcat(path, dp->d_name, sizeof(path)) >= sizeof(path)) {
+			weprintf("path too long\n");
+			return -1;
+		}
+
+		if (stat(path, &sb) < 0) {
+			weprintf("stat %s:", dp->d_name);
+			return -1;
+		}
+
+		if ((int)major(sb.st_rdev) == tty_maj &&
+		    (int)minor(sb.st_rdev) == tty_min) {
+			strlcpy(str, dp->d_name, n);
+			break;
+		}
+	}
+
+	if (closedir(dirp) < 0) {
+		weprintf("closedir /dev:");
+		return -1;
+	}
+
+	return 0;
 }

ps.c

@@ -70,7 +70,7 @@ psout(struct procstat *ps)
 	struct procstatus pstatus;
 	char cmdline[BUFSIZ], *cmd;
 	char buf[BUFSIZ];
-	char *ttystr, *myttystr;
+	char ttystr[PATH_MAX], *myttystr;
 	int tty_maj, tty_min;
 	uid_t myeuid;
 	unsigned sutime;
@@ -86,16 +86,13 @@ psout(struct procstat *ps)
 			return;
 
 	devtotty(ps->tty_nr, &tty_maj, &tty_min);
-	ttystr = ttytostr(tty_maj, tty_min);
+	ttytostr(tty_maj, tty_min, ttystr, sizeof(ttystr));
 
 	/* Only print processes that are associated with
 	 * a terminal and they are not session leaders */
-	if (flags & PS_aflag) {
-		if (ps->pid == ps->sid || ttystr[0] == '?') {
-			free(ttystr);
+	if (flags & PS_aflag)
+		if (ps->pid == ps->sid || ttystr[0] == '?')
 			return;
-		}
-	}
 
 	if (parsestatus(ps->pid, &pstatus) < 0)
 		return;
@@ -106,10 +103,8 @@ psout(struct procstat *ps)
 	if (!(flags & (PS_aflag | PS_Aflag | PS_dflag))) {
 		myttystr = ttyname(0);
 		if (myttystr) {
-			if (strcmp(myttystr + strlen("/dev/"), ttystr)) {
-				free(ttystr);
+			if (strcmp(myttystr + strlen("/dev/"), ttystr))
 				return;
-			}
 		} else {
 			/* The invoker has no controlling terminal - just
 			 * go ahead and print the processes anyway */
@@ -117,10 +112,8 @@ psout(struct procstat *ps)
 			ttystr[1] = '\0';
 		}
 		myeuid = geteuid();
-		if (myeuid != pstatus.euid) {
-			free(ttystr);
+		if (myeuid != pstatus.euid)
 			return;
-		}
 	}
 
 	sutime = (ps->stime + ps->utime) / sysconf(_SC_CLK_TCK);
@@ -166,7 +159,6 @@ psout(struct procstat *ps)
 		else
 			printf("%s\n", buf);
 	}
-	free(ttystr);
 }
 
 static void

util.h

@@ -50,4 +50,4 @@ size_t strlcpy(char *, const char *, size_t);
 
 /* tty.c */
 void devtotty(int, int *, int *);
-char *ttytostr(int, int);
+int ttytostr(int, int, char *, size_t);