Fix unsafe extraction of the OID part of a relation filename.

tglsfdc · tglsfdc · commit d0c0c894533f · 2018-03-25T15:15:40.000-04:00
Commit 8694cc9 did this randomly differently from other callers of parse_filename_for_nontemp_relation(). Perhaps unsurprisingly, the randomly different way is wrong; it fails to ensure the extracted string is null-terminated. Per buildfarm member skink. Discussion: https://postgr.es/m/14453.1522001792@sss.pgh.pa.us
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
@@ -1056,7 +1056,8 @@ sendDir(const char *path, int basepathlen, bool sizeonly, List *tablespaces,
 				 * If any other type of fork, check if there is an init fork
 				 * with the same OID. If so, the file can be excluded.
 				 */
-				strncpy(relOid, de->d_name, relOidChars);
+				memcpy(relOid, de->d_name, relOidChars);
+				relOid[relOidChars] = '\0';
 				snprintf(initForkFile, sizeof(initForkFile), "%s/%s_init",
 						 path, relOid);
 
