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291e517a4d
postgresql/contrib/pageinspect/gistfuncs.c
Michael Paquier 291e517a4d pageinspect: Add more sanity checks to prevent out-of-bound reads 
A couple of code paths use the special area on the page passed by the
function caller, expecting to find some data in it.  However, feeding
an incorrect page can lead to out-of-bound reads when trying to access
the page special area (like a heap page that has no special area,
leading PageGetSpecialPointer() to grab a pointer outside the allocated
page).

The functions used for hash and btree indexes have some protection
already against that, while some other functions using a relation OID
as argument would make sure that the access method involved is correct,
but functions taking in input a raw page without knowing the relation
the page is attached to would run into problems.

This commit improves the set of checks used in the code paths of BRIN,
btree (including one check if a leaf page is found with a non-zero
level), GIN and GiST to verify that the page given in input has a
special area size that fits with each access method, which is done
though PageGetSpecialSize(), becore calling PageGetSpecialPointer().

The scope of the checks done is limited to work with pages that one
would pass after getting a block with get_raw_page(), as it is possible
to craft byteas that could bypass existing code paths.  Having too many
checks would also impact the usability of pageinspect, as the existing
code is very useful to look at the content details in a corrupted page,
so the focus is really to avoid out-of-bound reads as this is never a
good thing even with functions whose execution is limited to
superusers.

The safest approach could be to rework the functions so as these fetch a
block using a relation OID and a block number, but there are also cases
where using a raw page is useful.

Tests are added to cover all the code paths that needed such checks, and
an error message for hash indexes is reworded to fit better with what
this commit adds.

Reported-By: Alexander Lakhin
Author: Julien Rouhaud, Michael Paquier
Discussion: https://postgr.es/m/16527-ef7606186f0610a1@postgresql.org
Discussion: https://postgr.es/m/561e187b-3549-c8d5-03f5-525c14e65bd0@postgrespro.ru
Backpatch-through: 10
2022-03-27 17:53:40 +09:00

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/*
* gistfuncs.c
* Functions to investigate the content of GiST indexes
*
* Copyright (c) 2014-2022, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/pageinspect/gistfuncs.c
*/
#include "postgres.h"
#include "access/gist.h"
#include "access/gist_private.h"
#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"
#include "storage/itemptr.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/pg_lsn.h"
#include "utils/varlena.h"
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)
Datum
gist_page_opaque_info(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
TupleDesc tupdesc;
Page page;
GISTPageOpaque opaq;
HeapTuple resultTuple;
Datum values[4];
bool nulls[4];
Datum flags[16];
int nflags = 0;
uint16 flagbits;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to use raw page functions")));
page = get_page_from_raw(raw_page);
/* verify the special space has the expected size */
if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GISTPageOpaqueData)))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid %s page", "GiST"),
errdetail("Expected special size %d, got %d.",
(int) MAXALIGN(sizeof(GISTPageOpaqueData)),
(int) PageGetSpecialSize(page))));
opaq = (GISTPageOpaque) PageGetSpecialPointer(page);
if (opaq->gist_page_id != GIST_PAGE_ID)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid %s page", "GiST"),
errdetail("Expected %08x, got %08x.",
GIST_PAGE_ID,
opaq->gist_page_id)));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
/* Convert the flags bitmask to an array of human-readable names */
flagbits = opaq->flags;
if (flagbits & F_LEAF)
flags[nflags++] = CStringGetTextDatum("leaf");
if (flagbits & F_DELETED)
flags[nflags++] = CStringGetTextDatum("deleted");
if (flagbits & F_TUPLES_DELETED)
flags[nflags++] = CStringGetTextDatum("tuples_deleted");
if (flagbits & F_FOLLOW_RIGHT)
flags[nflags++] = CStringGetTextDatum("follow_right");
if (flagbits & F_HAS_GARBAGE)
flags[nflags++] = CStringGetTextDatum("has_garbage");
flagbits &= ~(F_LEAF | F_DELETED | F_TUPLES_DELETED | F_FOLLOW_RIGHT | F_HAS_GARBAGE);
if (flagbits)
{
/* any flags we don't recognize are printed in hex */
flags[nflags++] = DirectFunctionCall1(to_hex32, Int32GetDatum(flagbits));
}
memset(nulls, 0, sizeof(nulls));
values[0] = LSNGetDatum(PageGetLSN(page));
values[1] = LSNGetDatum(GistPageGetNSN(page));
values[2] = Int64GetDatum(opaq->rightlink);
values[3] = PointerGetDatum(construct_array(flags, nflags,
TEXTOID,
-1, false, TYPALIGN_INT));
/* Build and return the result tuple. */
resultTuple = heap_form_tuple(tupdesc, values, nulls);
return HeapTupleGetDatum(resultTuple);
}
Datum
gist_page_items_bytea(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
Page page;
GISTPageOpaque opaq;
OffsetNumber offset;
OffsetNumber maxoff = InvalidOffsetNumber;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to use raw page functions")));
SetSingleFuncCall(fcinfo, 0);
page = get_page_from_raw(raw_page);
/* verify the special space has the expected size */
if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GISTPageOpaqueData)))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid %s page", "GiST"),
errdetail("Expected special size %d, got %d.",
(int) MAXALIGN(sizeof(GISTPageOpaqueData)),
(int) PageGetSpecialSize(page))));
opaq = (GISTPageOpaque) PageGetSpecialPointer(page);
if (opaq->gist_page_id != GIST_PAGE_ID)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid %s page", "GiST"),
errdetail("Expected %08x, got %08x.",
GIST_PAGE_ID,
opaq->gist_page_id)));
/* Avoid bogus PageGetMaxOffsetNumber() call with deleted pages */
if (GistPageIsDeleted(page))
elog(NOTICE, "page is deleted");
else
maxoff = PageGetMaxOffsetNumber(page);
for (offset = FirstOffsetNumber;
offset <= maxoff;
offset++)
{
Datum values[5];
bool nulls[5];
ItemId id;
IndexTuple itup;
bytea *tuple_bytea;
int tuple_len;
id = PageGetItemId(page, offset);
if (!ItemIdIsValid(id))
elog(ERROR, "invalid ItemId");
itup = (IndexTuple) PageGetItem(page, id);
tuple_len = IndexTupleSize(itup);
memset(nulls, 0, sizeof(nulls));
values[0] = DatumGetInt16(offset);
values[1] = ItemPointerGetDatum(&itup->t_tid);
values[2] = Int32GetDatum((int) IndexTupleSize(itup));
tuple_bytea = (bytea *) palloc(tuple_len + VARHDRSZ);
SET_VARSIZE(tuple_bytea, tuple_len + VARHDRSZ);
memcpy(VARDATA(tuple_bytea), itup, tuple_len);
values[3] = BoolGetDatum(ItemIdIsDead(id));
values[4] = PointerGetDatum(tuple_bytea);
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
}
return (Datum) 0;
}
Datum
gist_page_items(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
Oid indexRelid = PG_GETARG_OID(1);
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
Relation indexRel;
Page page;
OffsetNumber offset;
OffsetNumber maxoff = InvalidOffsetNumber;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to use raw page functions")));
SetSingleFuncCall(fcinfo, 0);
/* 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 */
if (GistPageIsDeleted(page))
elog(NOTICE, "page is deleted");
else
maxoff = PageGetMaxOffsetNumber(page);
for (offset = FirstOffsetNumber;
offset <= maxoff;
offset++)
{
Datum values[5];
bool nulls[5];
ItemId id;
IndexTuple itup;
Datum itup_values[INDEX_MAX_KEYS];
bool itup_isnull[INDEX_MAX_KEYS];
char *key_desc;
id = PageGetItemId(page, offset);
if (!ItemIdIsValid(id))
elog(ERROR, "invalid ItemId");
itup = (IndexTuple) PageGetItem(page, id);
index_deform_tuple(itup, RelationGetDescr(indexRel),
itup_values, itup_isnull);
memset(nulls, 0, sizeof(nulls));
values[0] = DatumGetInt16(offset);
values[1] = ItemPointerGetDatum(&itup->t_tid);
values[2] = Int32GetDatum((int) IndexTupleSize(itup));
values[3] = BoolGetDatum(ItemIdIsDead(id));
key_desc = BuildIndexValueDescription(indexRel, itup_values, itup_isnull);
if (key_desc)
values[4] = CStringGetTextDatum(key_desc);
else
{
values[4] = (Datum) 0;
nulls[4] = true;
}
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
}
relation_close(indexRel, AccessShareLock);
return (Datum) 0;
}
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