setaudit: Fix handling of numeric UIDs

The usage of strtoul() was incorrect.

Reviewed by:	csjp
MFC after:	2 weeks
Sponsored by:	Modirum MDPay
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D53671

usr.sbin/setaudit/setaudit.8

@@ -45,7 +45,7 @@ Use IPv4.
 .It Fl 6
 Use IPv6.
 .It Fl a Ar auid
-Audit user ID.
+Audit user ID or user name.
 .It Fl m Ar mask
 String representation of an audit mask.
 .It Fl s Ar source

usr.sbin/setaudit/setaudit.c

@@ -58,7 +58,7 @@ main(int argc, char *argv [])
 	auditinfo_addr_t aia;
 	struct addrinfo *res;
 	struct passwd *pwd;
-	char *aflag, *mflag, *sflag, *r, *prog;
+	char *aflag, *mflag, *sflag, *prog;
 	int ch, error;
 
 	aflag = mflag = sflag = NULL;
@@ -99,8 +99,10 @@ main(int argc, char *argv [])
 	if (aflag) {
 		pwd = getpwnam(aflag);
 		if (pwd == NULL) {
+			char *r;
+
 			aia.ai_auid = strtoul(aflag, &r, 10);
-			if (r != NULL)
+			if (*r != '\0')
 				errx(1, "%s: invalid user", aflag);
 		} else
 			aia.ai_auid = pwd->pw_uid;