Fix contrib/pgstattuple and contrib/pageinspect to prevent attempts to read

temporary tables of other sessions; that is unsafe because of the way our
buffer management works.  Per report from Stuart Bishop.
This is redundant with the bufmgr.c checks in HEAD, but not at all redundant
in the back branches.

4 files changed, 64 insertions, 2 deletions

diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index 794704af59..425e00a95f 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -1,5 +1,5 @@
 /*
- * $PostgreSQL:$ 
+ * $PostgreSQL$ 
  *
  *
  * btreefuncs.c
@@ -190,6 +190,16 @@ bt_page_stats(PG_FUNCTION_ARGS)
 		elog(ERROR, "relation \"%s\" is not a btree index",
 			 RelationGetRelationName(rel));
 
+	/*
+	 * Reject attempts to read non-local temporary relations; we would
+	 * be likely to get wrong data since we have no visibility into the
+	 * owning session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
 	if (blkno == 0)
 		elog(ERROR, "block 0 is a meta page");
 
@@ -298,6 +308,16 @@ bt_page_items(PG_FUNCTION_ARGS)
 			elog(ERROR, "relation \"%s\" is not a btree index",
 				 RelationGetRelationName(rel));
 
+		/*
+		 * Reject attempts to read non-local temporary relations; we would
+		 * be likely to get wrong data since we have no visibility into the
+		 * owning session's local buffers.
+		 */
+		if (RELATION_IS_OTHER_TEMP(rel))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot access temporary tables of other sessions")));
+
 		if (blkno == 0)
 			elog(ERROR, "block 0 is a meta page");
 
@@ -437,6 +457,16 @@ bt_metap(PG_FUNCTION_ARGS)
 		elog(ERROR, "relation \"%s\" is not a btree index",
 			 RelationGetRelationName(rel));
 
+	/*
+	 * Reject attempts to read non-local temporary relations; we would
+	 * be likely to get wrong data since we have no visibility into the
+	 * owning session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
 	buffer = ReadBuffer(rel, 0);
 	page = BufferGetPage(buffer);
 	metad = BTPageGetMeta(page);
diff --git a/contrib/pageinspect/rawpage.c b/contrib/pageinspect/rawpage.c
index 17ca7d7d37..08d61fab87 100644
--- a/contrib/pageinspect/rawpage.c
+++ b/contrib/pageinspect/rawpage.c
@@ -74,6 +74,16 @@ get_raw_page(PG_FUNCTION_ARGS)
 				 errmsg("cannot get raw page from composite type \"%s\"",
 						RelationGetRelationName(rel))));
 
+	/*
+	 * Reject attempts to read non-local temporary relations; we would
+	 * be likely to get wrong data since we have no visibility into the
+	 * owning session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
 	if (blkno >= RelationGetNumberOfBlocks(rel))
 		elog(ERROR, "block number %u is out of range for relation \"%s\"",
 			 blkno, RelationGetRelationName(rel));
diff --git a/contrib/pgstattuple/pgstatindex.c b/contrib/pgstattuple/pgstatindex.c
index 2793b2aaa0..56fa800538 100644
--- a/contrib/pgstattuple/pgstatindex.c
+++ b/contrib/pgstattuple/pgstatindex.c
@@ -1,5 +1,5 @@
 /*
- * $PostgreSQL:$ 
+ * $PostgreSQL$ 
  *
  *
  * pgstatindex
@@ -108,6 +108,16 @@ pgstatindex(PG_FUNCTION_ARGS)
 			 RelationGetRelationName(rel));
 
 	/*
+	 * Reject attempts to read non-local temporary relations; we would
+	 * be likely to get wrong data since we have no visibility into the
+	 * owning session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
+	/*
 	 * Read metapage
 	 */
 	{
@@ -262,6 +272,8 @@ pg_relpages(PG_FUNCTION_ARGS)
 	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
 	rel = relation_openrv(relrv, AccessShareLock);
 
+	/* note: this will work OK on non-local temp tables */
+
 	relpages = RelationGetNumberOfBlocks(rel);
 
 	relation_close(rel, AccessShareLock);
diff --git a/contrib/pgstattuple/pgstattuple.c b/contrib/pgstattuple/pgstattuple.c
index cce2676a33..1c475d6362 100644
--- a/contrib/pgstattuple/pgstattuple.c
+++ b/contrib/pgstattuple/pgstattuple.c
@@ -199,6 +199,16 @@ pgstat_relation(Relation rel, FunctionCallInfo fcinfo)
 {
 	const char *err;
 
+	/*
+	 * Reject attempts to read non-local temporary relations; we would
+	 * be likely to get wrong data since we have no visibility into the
+	 * owning session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
 	switch (rel->rd_rel->relkind)
 	{
 		case RELKIND_RELATION: