Avoid dangling pointer to relation name in RLS code path in DoCopy().

tglsfdc · tglsfdc · commit 943140d572ad · 2017-03-06T16:50:47.000-05:00
With RLS active, "COPY tab TO ..." failed under -DRELCACHE_FORCE_RELEASE, and would sometimes fail without that, because it used the relation name directly from the relcache as part of the parsetree it's building. That becomes a potentially-dangling pointer as soon as the relcache entry is closed, a bit further down. Typical symptom if the relcache entry chanced to get cleared would be "relation does not exist" error with a garbage relation name, or possibly a core dump; but if you were really truly unlucky, the COPY might copy from the wrong table. Per report from Andrew Dunstan that regression tests fail with -DRELCACHE_FORCE_RELEASE. The core tests now pass for me (but have not tried "make check-world" yet). Discussion: https://postgr.es/m/7b52f900-0579-cda9-ae2e-de5da17090e6@2ndQuadrant.com
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
@@ -938,7 +938,8 @@ DoCopy(const CopyStmt *stmt, const char *queryString, uint64 *processed)
 			 * relation which we have opened and locked.
 			 */
 			from = makeRangeVar(get_namespace_name(RelationGetNamespace(rel)),
-								RelationGetRelationName(rel), -1);
+								pstrdup(RelationGetRelationName(rel)),
+								-1);
 
 			/* Build query */
 			select = makeNode(SelectStmt);
