Fix issues found by Coverity scan.

- possible overflow of data offset calculation in wipe and
- dereferencing of pointer in a keyring error path.

lib/luks1/keymanage.c

@@ -1220,7 +1220,7 @@ int LUKS_wipe_header_areas(struct luks_phdr *hdr,
 
 	/* Wipe complete header, keyslots and padding aread with zeroes. */
 	offset = 0;
-	length = hdr->payloadOffset * SECTOR_SIZE;
+	length = (uint64_t)hdr->payloadOffset * SECTOR_SIZE;
 	wipe_block = 1024 * 1024;
 
 	/* On detached header or bogus header, wipe at least the first 4k */

lib/utils_keyring.c

@@ -133,6 +133,7 @@ int keyring_get_passphrase(const char *key_desc,
 
 	if (ret < 0) {
 		err = errno;
+		if (buf)
 			crypt_memzero(buf, len);
 		free(buf);
 		return -err;