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

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
index 5e38edfb703f08464ca83a5eefce82d4c1d2f058..db6ef783145d2893ebb87c388fefe5cb80483b1d 100644 (file)
--- 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);