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Overview
Comment:Avoid buffer overreads and false OOM error reports that could be caused by corrupted sample records in the sqlite_stat4 table.
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SHA1: 9f85b6a52a0b9b1524daa6f24d85257e7f591e95
User & Date: dan 2013-08-16 14:09:43
Context
2013-08-16
14:23
Add extra tests. No code changes. check-in: 949127d5 user: dan tags: sqlite_stat4
14:09
Avoid buffer overreads and false OOM error reports that could be caused by corrupted sample records in the sqlite_stat4 table. check-in: 9f85b6a5 user: dan tags: sqlite_stat4
13:34
Fix a potential segfault following an OOM while running ANALYZE. check-in: 01187978 user: drh tags: sqlite_stat4
Changes
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Changes to src/analyze.c.

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    ** the sqlite_stat4 table. In this case ignore stat3 data.  */
    nCol = pIdx->nSampleCol;
    if( bStat3 && nCol>1 ) continue;
    if( pIdx!=pPrevIdx ){
      initAvgEq(pPrevIdx);
      pPrevIdx = pIdx;
    }
    pSample = &pIdx->aSample[pIdx->nSample++];
    decodeIntArray((char*)sqlite3_column_text(pStmt,1), nCol, pSample->anEq, 0);
    decodeIntArray((char*)sqlite3_column_text(pStmt,2), nCol, pSample->anLt, 0);
    decodeIntArray((char*)sqlite3_column_text(pStmt,3), nCol, pSample->anDLt,0);







    pSample->n = sqlite3_column_bytes(pStmt, 4);
    pSample->p = sqlite3DbMallocZero(db, pSample->n);
    if( pSample->p==0 ){
      sqlite3_finalize(pStmt);
      return SQLITE_NOMEM;
    }
    memcpy(pSample->p, sqlite3_column_blob(pStmt, 4), pSample->n);

  }
  rc = sqlite3_finalize(pStmt);
  if( rc==SQLITE_OK ) initAvgEq(pPrevIdx);
  return rc;
}

/*







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    ** the sqlite_stat4 table. In this case ignore stat3 data.  */
    nCol = pIdx->nSampleCol;
    if( bStat3 && nCol>1 ) continue;
    if( pIdx!=pPrevIdx ){
      initAvgEq(pPrevIdx);
      pPrevIdx = pIdx;
    }
    pSample = &pIdx->aSample[pIdx->nSample];
    decodeIntArray((char*)sqlite3_column_text(pStmt,1), nCol, pSample->anEq, 0);
    decodeIntArray((char*)sqlite3_column_text(pStmt,2), nCol, pSample->anLt, 0);
    decodeIntArray((char*)sqlite3_column_text(pStmt,3), nCol, pSample->anDLt,0);

    /* Take a copy of the sample. Add two 0x00 bytes the end of the buffer.
    ** This is in case the sample record is corrupted. In that case, the
    ** sqlite3VdbeRecordCompare() may read up to two varints past the
    ** end of the allocated buffer before it realizes it is dealing with
    ** a corrupt record. Adding the two 0x00 bytes prevents this from causing
    ** a buffer overread.  */
    pSample->n = sqlite3_column_bytes(pStmt, 4);
    pSample->p = sqlite3DbMallocZero(db, pSample->n + 2);
    if( pSample->p==0 ){
      sqlite3_finalize(pStmt);
      return SQLITE_NOMEM;
    }
    memcpy(pSample->p, sqlite3_column_blob(pStmt, 4), pSample->n);
    pIdx->nSample++;
  }
  rc = sqlite3_finalize(pStmt);
  if( rc==SQLITE_OK ) initAvgEq(pPrevIdx);
  return rc;
}

/*

Changes to test/analyze9.test.

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do_execsql_test 5.1 {
  PRAGMA encoding = 'utf-16';
  CREATE TABLE t0(v);
  ANALYZE;
}

#-------------------------------------------------------------------------
# This was also crashing.
#
reset_db
do_execsql_test 6.1 {
  CREATE TABLE t1(a, b);
  CREATE INDEX i1 ON t1(a);
  CREATE INDEX i2 ON t1(b);
  INSERT INTO t1 VALUES(1, 1);
................................................................................
  INSERT INTO sqlite_stat4 SELECT * FROM x1;
  PRAGMA writable_schema = 0;
  ANALYZE sqlite_master;
}
do_execsql_test 6.2 {
  SELECT * FROM t1 WHERE a = 'abc';
}



























finish_test








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do_execsql_test 5.1 {
  PRAGMA encoding = 'utf-16';
  CREATE TABLE t0(v);
  ANALYZE;
}

#-------------------------------------------------------------------------
# This was also crashing (corrupt sqlite_stat4 table).
#
reset_db
do_execsql_test 6.1 {
  CREATE TABLE t1(a, b);
  CREATE INDEX i1 ON t1(a);
  CREATE INDEX i2 ON t1(b);
  INSERT INTO t1 VALUES(1, 1);
................................................................................
  INSERT INTO sqlite_stat4 SELECT * FROM x1;
  PRAGMA writable_schema = 0;
  ANALYZE sqlite_master;
}
do_execsql_test 6.2 {
  SELECT * FROM t1 WHERE a = 'abc';
}

#-------------------------------------------------------------------------
# The following tests experiment with adding corrupted records to the
# 'sample' column of the sqlite_stat4 table.
#
reset_db
sqlite3_db_config_lookaside db 0 0 0

do_execsql_test 7.1 {
  CREATE TABLE t1(a, b);
  CREATE INDEX i1 ON t1(a, b);
  INSERT INTO t1 VALUES(1, 1);
  INSERT INTO t1 VALUES(2, 2);
  INSERT INTO t1 VALUES(3, 3);
  INSERT INTO t1 VALUES(4, 4);
  INSERT INTO t1 VALUES(5, 5);
  ANALYZE;
  UPDATE sqlite_stat4 SET sample = X'' WHERE rowid = 1;
  ANALYZE sqlite_master;
}

do_execsql_test 7.2 {
  UPDATE sqlite_stat4 SET sample = X'FFFF';
  ANALYZE sqlite_master;
  SELECT * FROM t1 WHERE a = 1;
} {1 1}

finish_test