lib/nss.c: Verify that lines are complete

If a line doesn't have a '\n', this is a problem, and the line should be
rejected.

Also, remove the '\n' during the check (with stpsep()), because we don't
want it there when handling the string.

That stpsep() call had an error message, which I'm not sure what it
really meant.  I've removed it, because I don't know what better to do
with it.

Link: <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap03.html#tag_03_387>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

Author: alejandro-colomar

lib/nss.c

@@ -79,26 +79,23 @@ nss_init(const char *nsswitch_path) {
 	}
 	p = NULL;
 	while (getline(&line, &len, nssfp) != -1) {
+		if (stpsep(line, "\n") == NULL)
+			continue;
 		if (strprefix(line, "#"))
 			continue;
-		if (strlen(line) < 8)
+		if (strlen(line) < 7)
 			continue;
 		if (!strcaseprefix(line, "subid:"))
 			continue;
 		p = &line[6];
-		p = stpspn(p, " \t\n");
+		p = stpspn(p, " \t");
 		if (!streq(p, ""))
 			break;
 		p = NULL;
 	}
 	if (p == NULL) {
 		goto null_subid;
 	}
-	if (stpsep(p, "\n") == NULL) {
-		fprintf(log_get_logfd(), "No usable subid NSS module found, using files\n");
-		// subid_nss has to be null here, but to ease reviews:
-		goto null_subid;
-	}
 	stpsep(p, " \t");
 	if (streq(p, "files")) {
 		goto null_subid;