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.

1 files changed, 31 insertions, 1 deletions

diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index ab80b54500..85935b9990 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -1,5 +1,5 @@
 /*
- * $PostgreSQL: pgsql/contrib/pageinspect/btreefuncs.c,v 1.8 2008/05/17 01:28:19 adunstan Exp $ 
+ * $PostgreSQL: pgsql/contrib/pageinspect/btreefuncs.c,v 1.9 2009/03/31 22:54:31 tgl Exp $ 
  *
  *
  * 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);