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Overview
Comment:Remove an assert ("assert( subpage>0 )") from btree.c that may not be true for a corrupt database. Also add comments and other assert() statements to btree.c function moveToRoot(). (CVS 6886)
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SHA1: 3151dab9c78106217ec80ebadc666dfd11b42029
User & Date: danielk1977 2009-07-13 09:41:45
Context
2009-07-13
11:22
In sqlite3PagerWrite(), do not set the PGHDR_NEED_SYNC flag on a page if an IO error occured while attempting to journal it. (CVS 6887) check-in: b9be365d user: danielk1977 tags: trunk
09:41
Remove an assert ("assert( subpage>0 )") from btree.c that may not be true for a corrupt database. Also add comments and other assert() statements to btree.c function moveToRoot(). (CVS 6886) check-in: 3151dab9 user: danielk1977 tags: trunk
07:30
Remove a case from BtreeMovetoUnpacked() that is unreachable as of (6881). (CVS 6885) check-in: 39ce2097 user: danielk1977 tags: trunk
Changes
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Changes to src/btree.c.

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** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.683 2009/07/13 07:30:53 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
  releasePage(pCur->apPage[pCur->iPage]);
  pCur->iPage--;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
}

/*
** Move the cursor to the root page


















*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc = SQLITE_OK;
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;

  assert( cursorHoldsMutex(pCur) );
  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
  if( pCur->eState>=CURSOR_REQUIRESEEK ){
    if( pCur->eState==CURSOR_FAULT ){

      return pCur->skip;
    }
    sqlite3BtreeClearCursor(pCur);
  }

  if( pCur->iPage>=0 ){
    int i;
................................................................................
    ** return an SQLITE_CORRUPT error.  */
    assert( pCur->apPage[0]->intKey==1 || pCur->apPage[0]->intKey==0 );
    if( (pCur->pKeyInfo==0)!=pCur->apPage[0]->intKey ){
      return SQLITE_CORRUPT_BKPT;
    }
  }







  pRoot = pCur->apPage[0];
  assert( pRoot->pgno==pCur->pgnoRoot );


  pCur->aiIdx[0] = 0;
  pCur->info.nSize = 0;
  pCur->atLast = 0;
  pCur->validNKey = 0;

  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
    assert( pRoot->pgno==1 );
    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
    assert( subpage>0 );
    pCur->eState = CURSOR_VALID;
    rc = moveToChild(pCur, subpage);
  }else{
    pCur->eState = ((pRoot->nCell>0)?CURSOR_VALID:CURSOR_INVALID);
  }
  return rc;
}
................................................................................
    return rc;
  }
  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );

  pPage = pCur->apPage[pCur->iPage];
  assert( pPage->intKey || nKey>=0 );
  assert( pPage->leaf || !pPage->intKey );

  TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
          pCur->pgnoRoot, nKey, nData, pPage->pgno,
          loc==0 ? "overwrite" : "new entry"));
  assert( pPage->isInit );
  allocateTempSpace(pBt);
  newCell = pBt->pTmpSpace;
  if( newCell==0 ) return SQLITE_NOMEM;







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** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.684 2009/07/13 09:41:45 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
  releasePage(pCur->apPage[pCur->iPage]);
  pCur->iPage--;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
}

/*
** Move the cursor to point to the root page of its b-tree structure.
**
** If the table has a virtual root page, then the cursor is moved to point
** to the virtual root page instead of the actual root page. A table has a
** virtual root page when the actual root page contains no cells and a 
** single child page. This can only happen with the table rooted at page 1.
**
** If the b-tree structure is empty, the cursor state is set to 
** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
** cell located on the root (or virtual root) page and the cursor state
** is set to CURSOR_VALID.
**
** If this function returns successfully, it may be assumed that the
** page-header flags indicate that the [virtual] root-page is the expected 
** kind of b-tree page (i.e. if when opening the cursor the caller did not
** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
** indicating a table b-tree, or if the caller did specify a KeyInfo 
** structure the flags byte is set to 0x02 or 0x0A, indicating an index
** b-tree).
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc = SQLITE_OK;
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;

  assert( cursorHoldsMutex(pCur) );
  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
  if( pCur->eState>=CURSOR_REQUIRESEEK ){
    if( pCur->eState==CURSOR_FAULT ){
      assert( pCur->skip!=SQLITE_OK );
      return pCur->skip;
    }
    sqlite3BtreeClearCursor(pCur);
  }

  if( pCur->iPage>=0 ){
    int i;
................................................................................
    ** return an SQLITE_CORRUPT error.  */
    assert( pCur->apPage[0]->intKey==1 || pCur->apPage[0]->intKey==0 );
    if( (pCur->pKeyInfo==0)!=pCur->apPage[0]->intKey ){
      return SQLITE_CORRUPT_BKPT;
    }
  }

  /* Assert that the root page is of the correct type. This must be the
  ** case as the call to this function that loaded the root-page (either
  ** this call or a previous invocation) would have detected corruption 
  ** if the assumption were not true, and it is not possible for the flags 
  ** byte to have been modified while this cursor is holding a reference
  ** to the page.  */
  pRoot = pCur->apPage[0];
  assert( pRoot->pgno==pCur->pgnoRoot );
  assert( pRoot->isInit && (pCur->pKeyInfo==0)==pRoot->intKey );

  pCur->aiIdx[0] = 0;
  pCur->info.nSize = 0;
  pCur->atLast = 0;
  pCur->validNKey = 0;

  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;

    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);

    pCur->eState = CURSOR_VALID;
    rc = moveToChild(pCur, subpage);
  }else{
    pCur->eState = ((pRoot->nCell>0)?CURSOR_VALID:CURSOR_INVALID);
  }
  return rc;
}
................................................................................
    return rc;
  }
  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );

  pPage = pCur->apPage[pCur->iPage];
  assert( pPage->intKey || nKey>=0 );
  assert( pPage->leaf || !pPage->intKey );

  TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
          pCur->pgnoRoot, nKey, nData, pPage->pgno,
          loc==0 ? "overwrite" : "new entry"));
  assert( pPage->isInit );
  allocateTempSpace(pBt);
  newCell = pBt->pTmpSpace;
  if( newCell==0 ) return SQLITE_NOMEM;

Changes to test/corrupt.test.

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#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests to make sure SQLite does not crash or
# segfault if it sees a corrupt database file.
#
# $Id: corrupt.test,v 1.11 2009/07/11 17:39:42 danielk1977 Exp $

catch {file delete -force test.db test.db-journal test.bu}

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Construct a large database for testing.
................................................................................
  # This will fail, as the block modified the database image so that the
  # child page of the deleted cell is from a table (intkey) b-tree, not an
  # index b-tree as expected. At one point this was causing an assert()
  # to fail.
  catchsql { DELETE FROM t1 WHERE rowid = 3 }
} {1 {database disk image is malformed}}





















finish_test







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#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests to make sure SQLite does not crash or
# segfault if it sees a corrupt database file.
#
# $Id: corrupt.test,v 1.12 2009/07/13 09:41:45 danielk1977 Exp $

catch {file delete -force test.db test.db-journal test.bu}

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Construct a large database for testing.
................................................................................
  # This will fail, as the block modified the database image so that the
  # child page of the deleted cell is from a table (intkey) b-tree, not an
  # index b-tree as expected. At one point this was causing an assert()
  # to fail.
  catchsql { DELETE FROM t1 WHERE rowid = 3 }
} {1 {database disk image is malformed}}

do_test corrupt-5.1 {
  db close
  file delete -force test.db test.db-journal
  sqlite3 db test.db

  execsql { PRAGMA page_size = 1024 }
  set ct "CREATE TABLE t1(c0 "
  set i 0
  while {[string length $ct] < 950} { append ct ", c[incr i]" }
  append ct ")"
  execsql $ct
} {}

do_test corrupt-5.2 {
  db close
  hexio_write test.db 108 00000000 
  sqlite3 db test.db
  catchsql { SELECT * FROM sqlite_master }
} {1 {database disk image is malformed}}

finish_test