Check parsed integers for invalid or no digit errors

Verify that the string is not empty or does not contain trailing junk.

debian/changelog

@@ -22,6 +22,8 @@ dpkg (1.16.4) UNRELEASED; urgency=low
   * Remove obsolete --udeb dpkg-scanpackages option.
   * Add arm64 support to cputable. Closes: #672408
     Thanks Wookey <wookey@wookware.org>.
+  * Check parsed integers for invalid or no digit errors in start-stop-daemon
+    and update-alternatives.
 
   [ Updated man page translations ]
   * German (Helge Kreutzmann).

utils/start-stop-daemon.c

@@ -564,12 +564,14 @@ parse_signal(const char *sig_str, int *sig_num)
 static int
 parse_umask(const char *string, int *value_r)
 {
+	char *endptr;
+
 	if (!string[0])
 		return -1;
 
 	errno = 0;
-	*value_r = strtoul(string, NULL, 0);
-	if (errno)
+	*value_r = strtoul(string, &endptr, 0);
+	if (string == endptr || *endptr != '\0' || errno != 0)
 		return -1;
 	else
 		return 0;

utils/update-alternatives.c

@@ -1229,7 +1229,7 @@ alternative_parse_fileset(struct alternative *a, struct altdb_context *ctx)
 		prio_str = altdb_get_line(ctx, _("priority"));
 		prio = strtol(prio_str, &prio_end, 10);
 		/* XXX: Leak master_file/prio_str on non-fatal error */
-		if (*prio_end != '\0')
+		if (prio_str == prio_end || *prio_end != '\0')
 			ctx->bad_format(ctx, _("priority of %s: %s"),
 			                master_file, prio_str);
 		fs = fileset_new(master_file, prio);
@@ -2467,7 +2467,7 @@ main(int argc, char **argv)
 			if (strcmp(argv[i+1], argv[i+3]) == 0)
 				badusage(_("<link> and <path> can't be the same"));
 			prio = strtol(prio_str, &prio_end, 10);
-			if (*prio_end != '\0')
+			if (prio_str == prio_end || *prio_end != '\0')
 				badusage(_("priority must be an integer"));
 
 			a = alternative_new(argv[i + 2]);