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Add the btreeGetUnusedPage() routine to btree.c, and use it to detect content

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pages on the freelist and to cause that condition to trigger an SQLITE_CORRUPT.

FossilOrigin-Name: fe15d1f70360d6fef8ef1a111dd43e060d059623
This commit is contained in:
drh
2015-05-28 03:28:27 +00:00
parent 275fe3adf1
commit 7e8c6f1c2e
3 changed files with 48 additions and 26 deletions
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60
src/btree.c
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@@ -1723,10 +1723,10 @@ static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
** MemPage.aData elements if needed. See also: btreeGetUnusedPage().
**
** If the noContent flag is set, it means that we do not care about
** the content of the page at this time. So do not go to the disk
** If the PAGER_GET_NOCONTENT flag is set, it means that we do not care
** about the content of the page at this time. So do not go to the disk
** to fetch the content. Just fill in the content with zeros for now.
** If in the future we call sqlite3PagerWrite() on this page, that
** means we have started to be concerned about content and the disk
@@ -1828,6 +1828,36 @@ static void releasePage(MemPage *pPage){
}
}
/*
** Get an unused page.
**
** This works just like btreeGetPage() with the addition:
**
** * If the page is already in use for some other purpose, immediately
** release it and return an SQLITE_CURRUPT error.
** * Make sure the isInit flag is clear
*/
static int btreeGetUnusedPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int flags /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
){
int rc = btreeGetPage(pBt, pgno, ppPage, flags);
if( rc==SQLITE_OK ){
if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
releasePage(*ppPage);
*ppPage = 0;
return SQLITE_CORRUPT_BKPT;
}
(*ppPage)->isInit = 0;
}else{
*ppPage = 0;
}
return rc;
}
/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
@@ -5345,7 +5375,7 @@ static int allocateBtreePage(
if( iTrunk>mxPage ){
rc = SQLITE_CORRUPT_BKPT;
}else{
rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
rc = btreeGetUnusedPage(pBt, iTrunk, &pTrunk, 0);
}
if( rc ){
pTrunk = 0;
@@ -5410,7 +5440,7 @@ static int allocateBtreePage(
goto end_allocate_page;
}
testcase( iNewTrunk==mxPage );
rc = btreeGetPage(pBt, iNewTrunk, &pNewTrunk, 0);
rc = btreeGetUnusedPage(pBt, iNewTrunk, &pNewTrunk, 0);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
@@ -5490,7 +5520,7 @@ static int allocateBtreePage(
}
put4byte(&aData[4], k-1);
noContent = !btreeGetHasContent(pBt, *pPgno)? PAGER_GET_NOCONTENT : 0;
rc = btreeGetPage(pBt, *pPgno, ppPage, noContent);
rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, noContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
@@ -5538,7 +5568,7 @@ static int allocateBtreePage(
MemPage *pPg = 0;
TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetPage(pBt, pBt->nPage, &pPg, bNoContent);
rc = btreeGetUnusedPage(pBt, pBt->nPage, &pPg, bNoContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pPg->pDbPage);
releasePage(pPg);
@@ -5552,11 +5582,12 @@ static int allocateBtreePage(
*pPgno = pBt->nPage;
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetPage(pBt, *pPgno, ppPage, bNoContent);
rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, bNoContent);
if( rc ) return rc;
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
*ppPage = 0;
}
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
@@ -5566,17 +5597,8 @@ static int allocateBtreePage(
end_allocate_page:
releasePage(pTrunk);
releasePage(pPrevTrunk);
if( rc==SQLITE_OK ){
if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
releasePage(*ppPage);
*ppPage = 0;
return SQLITE_CORRUPT_BKPT;
}
(*ppPage)->isInit = 0;
}else{
*ppPage = 0;
}
assert( rc!=SQLITE_OK || sqlite3PagerIswriteable((*ppPage)->pDbPage) );
assert( rc!=SQLITE_OK || sqlite3PagerPageRefcount((*ppPage)->pDbPage)<=1 );
assert( rc!=SQLITE_OK || (*ppPage)->isInit==0 );
return rc;
}