pageinspect: Fix handling of page sizes and AM types

This commit fixes a set of issues related to the use of the SQL
functions in this module when the caller is able to pass down raw page
data as input argument:
- The page size check was fuzzy in a couple of places, sometimes
looking after only a sub-range, but what we are looking for is an exact
match on BLCKSZ.  After considering a few options here, I have settled
down to do a generalization of get_page_from_raw().  Most of the SQL
functions already used that, and this is not strictly required if not
accessing an 8-byte-wide value from a raw page, but this feels safer in
the long run for alignment-picky environment, particularly if a code
path begins to access such values.  This also reduces the number of
strings that need to be translated.
- The BRIN function brin_page_items() uses a Relation but it did not
check the access method of the opened index, potentially leading to
crashes.  All the other functions in need of a Relation already did
that.
- Some code paths could fail on elog(), but we should to use ereport()
for failures that can be triggered by the user.

Tests are added to stress all the cases that are fixed as of this
commit, with some junk raw pages (\set VERBOSITY ensures that this works
across all page sizes) and unexpected index types when functions open
relations.

Author: Michael Paquier, Justin Prysby
Discussion: https://postgr.es/m/20220218030020.GA1137@telsasoft.com
Backpatch-through: 10

Author: michaelpq

contrib/pageinspect/brinfuncs.c

@@ -16,6 +16,7 @@
 #include "access/brin_tuple.h"
 #include "access/htup_details.h"
 #include "catalog/index.h"
+#include "catalog/pg_am_d.h"
 #include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
@@ -31,6 +32,8 @@ PG_FUNCTION_INFO_V1(brin_page_items);
 PG_FUNCTION_INFO_V1(brin_metapage_info);
 PG_FUNCTION_INFO_V1(brin_revmap_data);
 
+#define IS_BRIN(r) ((r)->rd_rel->relam == BRIN_AM_OID)
+
 typedef struct brin_column_state
 {
 	int			nstored;
@@ -45,23 +48,15 @@ Datum
 brin_page_type(PG_FUNCTION_ARGS)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
-	Page		page = VARDATA(raw_page);
-	int			raw_page_size;
+	Page		page;
 	char	   *type;
 
 	if (!superuser())
 		ereport(ERROR,
 				(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"),
-				 errdetail("Expected size %d, got %d",
-						   BLCKSZ, raw_page_size)));
+	page = get_page_from_raw(raw_page);
 
 	switch (BrinPageType(page))
 	{
@@ -89,19 +84,7 @@ brin_page_type(PG_FUNCTION_ARGS)
 static Page
 verify_brin_page(bytea *raw_page, uint16 type, const char *strtype)
 {
-	Page		page;
-	int			raw_page_size;
-
-	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-
-	if (raw_page_size != BLCKSZ)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("input page too small"),
-				 errdetail("Expected size %d, got %d",
-						   BLCKSZ, raw_page_size)));
-
-	page = VARDATA(raw_page);
+	Page		page = get_page_from_raw(raw_page);
 
 	/* verify the special space says this page is what we want */
 	if (BrinPageType(page) != type)
@@ -143,6 +126,13 @@ brin_page_items(PG_FUNCTION_ARGS)
 	SetSingleFuncCall(fcinfo, 0);
 
 	indexRel = index_open(indexRelid, AccessShareLock);
+
+	if (!IS_BRIN(indexRel))
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(indexRel), "BRIN")));
+
 	bdesc = brin_build_desc(indexRel);
 
 	/* minimally verify the page we got */

contrib/pageinspect/btreefuncs.c

@@ -206,8 +206,10 @@ bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
 	rel = relation_openrv(relrv, AccessShareLock);
 
 	if (!IS_INDEX(rel) || !IS_BTREE(rel))
-		elog(ERROR, "relation \"%s\" is not a btree index",
-			 RelationGetRelationName(rel));
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(rel), "btree")));
 
 	/*
 	 * Reject attempts to read non-local temporary relations; we would be
@@ -476,8 +478,10 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
 		rel = relation_openrv(relrv, AccessShareLock);
 
 		if (!IS_INDEX(rel) || !IS_BTREE(rel))
-			elog(ERROR, "relation \"%s\" is not a btree index",
-				 RelationGetRelationName(rel));
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("\"%s\" is not a %s index",
+							RelationGetRelationName(rel), "btree")));
 
 		/*
 		 * Reject attempts to read non-local temporary relations; we would be
@@ -588,7 +592,6 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
 	Datum		result;
 	FuncCallContext *fctx;
 	struct user_args *uargs;
-	int			raw_page_size;
 
 	if (!superuser())
 		ereport(ERROR,
@@ -601,19 +604,12 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
 		MemoryContext mctx;
 		TupleDesc	tupleDesc;
 
-		raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-
-		if (raw_page_size < SizeOfPageHeaderData)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("input page too small (%d bytes)", raw_page_size)));
-
 		fctx = SRF_FIRSTCALL_INIT();
 		mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
 
 		uargs = palloc(sizeof(struct user_args));
 
-		uargs->page = VARDATA(raw_page);
+		uargs->page = get_page_from_raw(raw_page);
 
 		uargs->offset = FirstOffsetNumber;
 
@@ -698,8 +694,10 @@ bt_metap(PG_FUNCTION_ARGS)
 	rel = relation_openrv(relrv, AccessShareLock);
 
 	if (!IS_INDEX(rel) || !IS_BTREE(rel))
-		elog(ERROR, "relation \"%s\" is not a btree index",
-			 RelationGetRelationName(rel));
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(rel), "btree")));
 
 	/*
 	 * Reject attempts to read non-local temporary relations; we would be

contrib/pageinspect/expected/brin.out

@@ -48,4 +48,8 @@ SELECT * FROM brin_page_items(get_raw_page('test1_a_idx', 2), 'test1_a_idx')
           1 |      0 |      1 | f        | f        | f           | {1 .. 1}
 (1 row)
 
+-- Failure for non-BRIN index.
+CREATE INDEX test1_a_btree ON test1 (a);
+SELECT brin_page_items(get_raw_page('test1_a_btree', 0), 'test1_a_btree');
+ERROR:  "test1_a_btree" is not a BRIN index
 DROP TABLE test1;

contrib/pageinspect/expected/btree.out

@@ -70,4 +70,19 @@ tids       |
 
 SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 2));
 ERROR:  block number 2 is out of range for relation "test1_a_idx"
+-- Failure when using a non-btree index.
+CREATE INDEX test1_a_hash ON test1 USING hash(a);
+SELECT bt_metap('test1_a_hash');
+ERROR:  "test1_a_hash" is not a btree index
+SELECT bt_page_stats('test1_a_hash', 0);
+ERROR:  "test1_a_hash" is not a btree index
+SELECT bt_page_items('test1_a_hash', 0);
+ERROR:  "test1_a_hash" is not a btree index
+-- Failure with incorrect page size
+-- Suppress the DETAIL message, to allow the tests to work across various
+-- page sizes.
+\set VERBOSITY terse
+SELECT bt_page_items('aaa'::bytea);
+ERROR:  invalid page size
+\set VERBOSITY default
 DROP TABLE test1;

contrib/pageinspect/expected/gin.out

@@ -36,3 +36,14 @@ FROM gin_leafpage_items(get_raw_page('test1_y_idx',
 ?column? | t
 
 DROP TABLE test1;
+-- Failure with incorrect page size
+-- Suppress the DETAIL message, to allow the tests to work across various
+-- page sizes.
+\set VERBOSITY terse
+SELECT gin_leafpage_items('aaa'::bytea);
+ERROR:  invalid page size
+SELECT gin_metapage_info('bbb'::bytea);
+ERROR:  invalid page size
+SELECT gin_page_opaque_info('ccc'::bytea);
+ERROR:  invalid page size
+\set VERBOSITY default

contrib/pageinspect/expected/gist.out

@@ -64,4 +64,19 @@ SELECT itemoffset, ctid, itemlen FROM gist_page_items_bytea(get_raw_page('test_g
           6 | (6,65535) |      40
 (6 rows)
 
+-- Failure with non-GiST index.
+CREATE INDEX test_gist_btree on test_gist(t);
+SELECT gist_page_items(get_raw_page('test_gist_btree', 0), 'test_gist_btree');
+ERROR:  "test_gist_btree" is not a GiST index
+-- Failure with incorrect page size
+-- Suppress the DETAIL message, to allow the tests to work across various
+-- page sizes.
+\set VERBOSITY terse
+SELECT gist_page_items_bytea('aaa'::bytea);
+ERROR:  invalid page size
+SELECT gist_page_items('aaa'::bytea, 'test_gist_idx'::regclass);
+ERROR:  invalid page size
+SELECT gist_page_opaque_info('aaa'::bytea);
+ERROR:  invalid page size
+\set VERBOSITY default
 DROP TABLE test_gist;

contrib/pageinspect/expected/hash.out

@@ -163,4 +163,21 @@ SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 4));
 
 SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 5));
 ERROR:  page is not a hash bucket or overflow page
+-- Failure with non-hash index
+CREATE INDEX test_hash_a_btree ON test_hash USING btree (a);
+SELECT hash_bitmap_info('test_hash_a_btree', 0);
+ERROR:  "test_hash_a_btree" is not a hash index
+-- Failure with incorrect page size
+-- Suppress the DETAIL message, to allow the tests to work across various
+-- page sizes.
+\set VERBOSITY terse
+SELECT hash_metapage_info('aaa'::bytea);
+ERROR:  invalid page size
+SELECT hash_page_items('bbb'::bytea);
+ERROR:  invalid page size
+SELECT hash_page_stats('ccc'::bytea);
+ERROR:  invalid page size
+SELECT hash_page_type('ddd'::bytea);
+ERROR:  invalid page size
+\set VERBOSITY default
 DROP TABLE test_hash;

contrib/pageinspect/expected/page.out

@@ -207,3 +207,14 @@ select tuple_data_split('test8'::regclass, t_data, t_infomask, t_infomask2, t_bi
 (1 row)
 
 drop table test8;
+-- Failure with incorrect page size
+-- Suppress the DETAIL message, to allow the tests to work across various
+-- page sizes.
+\set VERBOSITY terse
+SELECT fsm_page_contents('aaa'::bytea);
+ERROR:  invalid page size
+SELECT page_checksum('bbb'::bytea, 0);
+ERROR:  invalid page size
+SELECT page_header('ccc'::bytea);
+ERROR:  invalid page size
+\set VERBOSITY default

contrib/pageinspect/fsmfuncs.c

@@ -36,6 +36,7 @@ fsm_page_contents(PG_FUNCTION_ARGS)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
 	StringInfoData sinfo;
+	Page		page;
 	FSMPage		fsmpage;
 	int			i;
 
@@ -44,7 +45,8 @@ fsm_page_contents(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("must be superuser to use raw page functions")));
 
-	fsmpage = (FSMPage) PageGetContents(VARDATA(raw_page));
+	page = get_page_from_raw(raw_page);
+	fsmpage = (FSMPage) PageGetContents(page);
 
 	initStringInfo(&sinfo);
 

contrib/pageinspect/gistfuncs.c

@@ -14,6 +14,7 @@
 #include "access/htup.h"
 #include "access/relation.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_am_d.h"
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "pageinspect.h"
@@ -28,6 +29,8 @@ PG_FUNCTION_INFO_V1(gist_page_opaque_info);
 PG_FUNCTION_INFO_V1(gist_page_items);
 PG_FUNCTION_INFO_V1(gist_page_items_bytea);
 
+#define IS_GIST(r) ((r)->rd_rel->relam == GIST_AM_OID)
+
 #define ItemPointerGetDatum(X)	 PointerGetDatum(X)
 
 
@@ -174,6 +177,12 @@ gist_page_items(PG_FUNCTION_ARGS)
 	/* Open the relation */
 	indexRel = index_open(indexRelid, AccessShareLock);
 
+	if (!IS_GIST(indexRel))
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(indexRel), "GiST")));
+
 	page = get_page_from_raw(raw_page);
 
 	/* Avoid bogus PageGetMaxOffsetNumber() call with deleted pages */

contrib/pageinspect/hashfuncs.c

@@ -417,8 +417,10 @@ hash_bitmap_info(PG_FUNCTION_ARGS)
 	indexRel = index_open(indexRelid, AccessShareLock);
 
 	if (!IS_HASH(indexRel))
-		elog(ERROR, "relation \"%s\" is not a hash index",
-			 RelationGetRelationName(indexRel));
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(indexRel), "hash")));
 
 	if (RELATION_IS_OTHER_TEMP(indexRel))
 		ereport(ERROR,

contrib/pageinspect/rawpage.c

@@ -246,7 +246,6 @@ Datum
 page_header(PG_FUNCTION_ARGS)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
-	int			raw_page_size;
 
 	TupleDesc	tupdesc;
 
@@ -263,18 +262,7 @@ page_header(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("must be superuser to use raw page functions")));
 
-	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-
-	/*
-	 * Check that enough data was supplied, so that we don't try to access
-	 * fields outside the supplied buffer.
-	 */
-	if (raw_page_size < SizeOfPageHeaderData)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("input page too small (%d bytes)", raw_page_size)));
-
-	page = (PageHeader) VARDATA(raw_page);
+	page = (PageHeader) get_page_from_raw(raw_page);
 
 	/* Build a tuple descriptor for our result type */
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
@@ -350,8 +338,7 @@ page_checksum_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
 {
 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
 	int64		blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
-	int			raw_page_size;
-	PageHeader	page;
+	Page		page;
 
 	if (!superuser())
 		ereport(ERROR,
@@ -363,17 +350,7 @@ page_checksum_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("invalid block number")));
 
-	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
-
-	/*
-	 * Check that the supplied page is of the right size.
-	 */
-	if (raw_page_size != BLCKSZ)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("incorrect size of input page (%d bytes)", raw_page_size)));
-
-	page = (PageHeader) VARDATA(raw_page);
+	page = get_page_from_raw(raw_page);
 
 	PG_RETURN_INT16(pg_checksum_page((char *) page, blkno));
 }

contrib/pageinspect/sql/brin.sql

@@ -15,4 +15,8 @@ SELECT * FROM brin_revmap_data(get_raw_page('test1_a_idx', 1)) LIMIT 5;
 SELECT * FROM brin_page_items(get_raw_page('test1_a_idx', 2), 'test1_a_idx')
     ORDER BY blknum, attnum LIMIT 5;
 
+-- Failure for non-BRIN index.
+CREATE INDEX test1_a_btree ON test1 (a);
+SELECT brin_page_items(get_raw_page('test1_a_btree', 0), 'test1_a_btree');
+
 DROP TABLE test1;

contrib/pageinspect/sql/btree.sql

@@ -21,4 +21,17 @@ SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 0));
 SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 1));
 SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 2));
 
+-- Failure when using a non-btree index.
+CREATE INDEX test1_a_hash ON test1 USING hash(a);
+SELECT bt_metap('test1_a_hash');
+SELECT bt_page_stats('test1_a_hash', 0);
+SELECT bt_page_items('test1_a_hash', 0);
+
+-- Failure with incorrect page size
+-- Suppress the DETAIL message, to allow the tests to work across various
+-- page sizes.
+\set VERBOSITY terse
+SELECT bt_page_items('aaa'::bytea);
+\set VERBOSITY default
+
 DROP TABLE test1;