pageinspect: Fix unaligned struct access in GIN functions

petere · petere · commit 84ad68d64522 · 2016-11-04T10:05:37.000-04:00
The raw page data that is passed into the functions will not be aligned
at 8-byte boundaries.  Casting that to a struct and accessing int64
fields will result in unaligned access.  On most platforms, you get away
with it, but it will result on a crash on pickier platforms such as ia64
and sparc64.
diff --git a/contrib/pageinspect/ginfuncs.c b/contrib/pageinspect/ginfuncs.c
@@ -28,11 +28,31 @@ PG_FUNCTION_INFO_V1(gin_metapage_info);
 PG_FUNCTION_INFO_V1(gin_page_opaque_info);
 PG_FUNCTION_INFO_V1(gin_leafpage_items);
 
+
+static Page
+get_page_from_raw(bytea *raw_page)
+{
+	int			raw_page_size;
+	Page		page;
+
+	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
+	if (raw_page_size < BLCKSZ)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("input page too small (%d bytes)", raw_page_size)));
+
+	/* make a copy so that the page is properly aligned for struct access */
+	page = palloc(raw_page_size);
+	memcpy(page, VARDATA(raw_page), raw_page_size);
+
+	return page;
+}
+
+
 Datum
 gin_metapage_info(PG_FUNCTION_ARGS)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
-	int			raw_page_size;
 	TupleDesc	tupdesc;
 	Page		page;
 	GinPageOpaque opaq;
@@ -46,12 +66,7 @@ gin_metapage_info(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 (errmsg("must be superuser to use raw page functions"))));
 
-	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-	if (raw_page_size < BLCKSZ)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("input page too small (%d bytes)", raw_page_size)));
-	page = VARDATA(raw_page);
+	page = get_page_from_raw(raw_page);
 
 	opaq = (GinPageOpaque) PageGetSpecialPointer(page);
 	if (opaq->flags != GIN_META)
@@ -94,7 +109,6 @@ Datum
 gin_page_opaque_info(PG_FUNCTION_ARGS)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
-	int			raw_page_size;
 	TupleDesc	tupdesc;
 	Page		page;
 	GinPageOpaque opaq;
@@ -110,12 +124,7 @@ gin_page_opaque_info(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 (errmsg("must be superuser to use raw page functions"))));
 
-	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-	if (raw_page_size < BLCKSZ)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("input page too small (%d bytes)", raw_page_size)));
-	page = VARDATA(raw_page);
+	page = get_page_from_raw(raw_page);
 
 	opaq = (GinPageOpaque) PageGetSpecialPointer(page);
 
@@ -173,7 +182,6 @@ Datum
 gin_leafpage_items(PG_FUNCTION_ARGS)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
-	int			raw_page_size;
 	FuncCallContext *fctx;
 	gin_leafpage_items_state *inter_call_data;
 
@@ -182,20 +190,14 @@ gin_leafpage_items(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 (errmsg("must be superuser to use raw page functions"))));
 
-	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-
 	if (SRF_IS_FIRSTCALL())
 	{
 		TupleDesc	tupdesc;
 		MemoryContext mctx;
 		Page		page;
 		GinPageOpaque opaq;
 
-		if (raw_page_size < BLCKSZ)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				  errmsg("input page too small (%d bytes)", raw_page_size)));
-		page = VARDATA(raw_page);
+		page = get_page_from_raw(raw_page);
 
 		if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GinPageOpaqueData)))
 			ereport(ERROR,
