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Add defenses to btree and hash index AMs to do simple sanity checks

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on every index page they read; in particular to catch the case of an
all-zero page, which PageHeaderIsValid allows to pass.  It turns out
hash already had this idea, but it was just Assert()ing things rather
than doing a straight error check, and the Asserts were partially
redundant with PageHeaderIsValid anyway.  Per recent failure example
from Jim Nasby.  (gist still needs the same treatment.)
This commit is contained in:
Tom Lane
2005-11-06 19:29:01 +00:00
parent 18691d8ee3
commit 766dc45d9f
11 changed files with 147 additions and 79 deletions
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46
src/backend/access/nbtree/nbtpage.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.88 2005/10/15 02:49:09 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.89 2005/11/06 19:29:00 tgl Exp $
*
* NOTES
* Postgres btree pages look like ordinary relation pages. The opaque
@@ -222,8 +222,6 @@ _bt_getroot(Relation rel, int access)
rootbuf = _bt_getbuf(rel, P_NEW, BT_WRITE);
rootblkno = BufferGetBlockNumber(rootbuf);
rootpage = BufferGetPage(rootbuf);
_bt_pageinit(rootpage, BufferGetPageSize(rootbuf));
rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
rootopaque->btpo_prev = rootopaque->btpo_next = P_NONE;
rootopaque->btpo_flags = (BTP_LEAF | BTP_ROOT);
@@ -405,14 +403,50 @@ _bt_gettrueroot(Relation rel)
return rootbuf;
}
/*
* _bt_checkpage() -- Verify that a freshly-read page looks sane.
*/
void
_bt_checkpage(Relation rel, Buffer buf)
{
Page page = BufferGetPage(buf);
/*
* ReadBuffer verifies that every newly-read page passes PageHeaderIsValid,
* which means it either contains a reasonably sane page header or is
* all-zero. We have to defend against the all-zero case, however.
*/
if (PageIsNew(page))
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg("index \"%s\" contains unexpected zero page at block %u",
RelationGetRelationName(rel),
BufferGetBlockNumber(buf)),
errhint("Please REINDEX it.")));
/*
* Additionally check that the special area looks sane.
*/
if (((PageHeader) (page))->pd_special !=
(BLCKSZ - MAXALIGN(sizeof(BTPageOpaqueData))))
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg("index \"%s\" contains corrupted page at block %u",
RelationGetRelationName(rel),
BufferGetBlockNumber(buf)),
errhint("Please REINDEX it.")));
}
/*
* _bt_getbuf() -- Get a buffer by block number for read or write.
*
* blkno == P_NEW means to get an unallocated index page.
* blkno == P_NEW means to get an unallocated index page. The page
* will be initialized before returning it.
*
* When this routine returns, the appropriate lock is set on the
* requested buffer and its reference count has been incremented
* (ie, the buffer is "locked and pinned").
* (ie, the buffer is "locked and pinned"). Also, we apply
* _bt_checkpage to sanity-check the page (except in P_NEW case).
*/
Buffer
_bt_getbuf(Relation rel, BlockNumber blkno, int access)
@@ -424,6 +458,7 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
/* Read an existing block of the relation */
buf = ReadBuffer(rel, blkno);
LockBuffer(buf, access);
_bt_checkpage(rel, buf);
}
else
{
@@ -538,6 +573,7 @@ _bt_relandgetbuf(Relation rel, Buffer obuf, BlockNumber blkno, int access)
LockBuffer(obuf, BUFFER_LOCK_UNLOCK);
buf = ReleaseAndReadBuffer(obuf, rel, blkno);
LockBuffer(buf, access);
_bt_checkpage(rel, buf);
return buf;
}