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mariadb/sql/rpl_utility.cc
Brandon Nesterenko 080480c52d MDEV-40646: Undersized Table_map Metadata can Crash Slave 
A slave can crash or leak heap content when its master sends a Table_map
event that declares columns whose types need more field metadata than
the event carries. Building its description of the table, the slave
reads past the end of the field metadata the event holds. The bytes
beyond the buffer are decoded as column metadata.

A Table_map event carries a column count, one type byte per column,
and a block of field metadata. A column's type fixes how many metadata
bytes it consumes: two for the string, enum, set, bit, varchar, and
decimal types, one for the blob, float, and high precision temporal
types, none for the rest. The master writes exactly that many bytes
per column, so the metadata block a well formed event carries is the
sum over its columns. The slave sizes the metadata block from the
event and, while building its table_def, walks the columns in order
and reads each type's metadata bytes from that block.

The slave checked only that the metadata block was no larger than two
bytes per column. It never checked the block against the column types
themselves. table_def() then walked every declared column and indexed
the metadata block for each, so a column whose type needed metadata
the block did not hold read past the end of it. A column count large
enough carried that read far past the allocation.

The Table_map reader now sums the metadata the declared column types
consume and rejects the event when the block is smaller than that
sum, so is_valid() reports the event as invalid and the SQL thread
stops with a relay log read failure before any column is decoded. A
block larger than the sum is still accepted, because every consumer
reads only the bytes the types call for. A column type this slave
does not recognize counts as zero in the sum, so Table_map events
from a newer master using such a type still parse. A Table_map whose
metadata cannot cover its column types now stops the slave with an
error instead of reading past the buffer.

Note that the regression test does not crash a regular debug build;
an ASAN build is required to show the invalid memory access.  The 24
column table map it injects overruns the metadata allocation by a
bounded amount that lands in mapped heap, which a debug build reads
without faulting and then stops the SQL thread with
ER_SLAVE_CONVERSION_FAILED on the column type mismatch.

Reviewed-by: Kristian Nielsen <knielsen@knielsen-hq.org>
Signed-off-by: Brandon Nesterenko <brandon.nesterenko@mariadb.com>
2026-08-11 11:29:34 -06:00

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/* Copyright (c) 2006, 2013, Oracle and/or its affiliates.
Copyright (c) 2011, 2013, Monty Program Ab
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
#include "mariadb.h"
#include <my_bit.h>
#include "rpl_utility.h"
#include "log_event.h"
/*********************************************************************
* table_def member definitions *
*********************************************************************/
/*
This function returns the field size in raw bytes based on the type
and the encoded field data from the master's raw data.
*/
uint32 table_def::calc_field_size(uint col, uchar *master_data) const
{
uint32 length= 0;
switch (type(col)) {
case MYSQL_TYPE_NEWDECIMAL:
length= my_decimal_get_binary_size(m_field_metadata[col] >> 8,
m_field_metadata[col] & 0xff);
break;
case MYSQL_TYPE_DECIMAL:
case MYSQL_TYPE_FLOAT:
case MYSQL_TYPE_DOUBLE:
length= m_field_metadata[col];
break;
/*
The cases for SET and ENUM are include for completeness, however
both are mapped to type MYSQL_TYPE_STRING and their real types
are encoded in the field metadata.
*/
case MYSQL_TYPE_SET:
case MYSQL_TYPE_ENUM:
case MYSQL_TYPE_STRING:
{
uchar type= m_field_metadata[col] >> 8U;
if ((type == MYSQL_TYPE_SET) || (type == MYSQL_TYPE_ENUM))
length= m_field_metadata[col] & 0x00ff;
else
{
/*
We are reading the actual size from the master_data record
because this field has the actual lengh stored in the first
byte.
*/
length= (uint) *master_data + 1;
DBUG_ASSERT(length != 0);
}
break;
}
case MYSQL_TYPE_YEAR:
case MYSQL_TYPE_TINY:
length= 1;
break;
case MYSQL_TYPE_SHORT:
length= 2;
break;
case MYSQL_TYPE_INT24:
length= 3;
break;
case MYSQL_TYPE_LONG:
length= 4;
break;
#ifdef HAVE_LONG_LONG
case MYSQL_TYPE_LONGLONG:
length= 8;
break;
#endif
case MYSQL_TYPE_NULL:
length= 0;
break;
case MYSQL_TYPE_NEWDATE:
length= 3;
break;
case MYSQL_TYPE_DATE:
case MYSQL_TYPE_TIME:
length= 3;
break;
case MYSQL_TYPE_TIME2:
length= my_time_binary_length(m_field_metadata[col]);
break;
case MYSQL_TYPE_TIMESTAMP:
length= 4;
break;
case MYSQL_TYPE_TIMESTAMP2:
length= my_timestamp_binary_length(m_field_metadata[col]);
break;
case MYSQL_TYPE_DATETIME:
length= 8;
break;
case MYSQL_TYPE_DATETIME2:
length= my_datetime_binary_length(m_field_metadata[col]);
break;
case MYSQL_TYPE_BIT:
{
/*
Decode the size of the bit field from the master.
from_len is the length in bytes from the master
from_bit_len is the number of extra bits stored in the master record
If from_bit_len is not 0, add 1 to the length to account for accurate
number of bytes needed.
*/
uint from_len= (m_field_metadata[col] >> 8U) & 0x00ff;
uint from_bit_len= m_field_metadata[col] & 0x00ff;
DBUG_ASSERT(from_bit_len <= 7);
length= from_len + ((from_bit_len > 0) ? 1 : 0);
break;
}
case MYSQL_TYPE_VARCHAR:
case MYSQL_TYPE_VARCHAR_COMPRESSED:
{
length= m_field_metadata[col] > 255 ? 2 : 1; // c&p of Field_varstring::data_length()
length+= length == 1 ? (uint32) *master_data : uint2korr(master_data);
break;
}
case MYSQL_TYPE_TINY_BLOB:
case MYSQL_TYPE_MEDIUM_BLOB:
case MYSQL_TYPE_LONG_BLOB:
case MYSQL_TYPE_BLOB:
case MYSQL_TYPE_BLOB_COMPRESSED:
case MYSQL_TYPE_GEOMETRY:
{
/*
Compute the length of the data. We cannot use get_length() here
since it is dependent on the specific table (and also checks the
packlength using the internal 'table' pointer) and replication
is using a fixed format for storing data in the binlog.
*/
switch (m_field_metadata[col]) {
case 1:
length= *master_data;
break;
case 2:
length= uint2korr(master_data);
break;
case 3:
length= uint3korr(master_data);
break;
case 4:
length= uint4korr(master_data);
break;
default:
DBUG_ASSERT(0); // Should not come here
break;
}
length+= m_field_metadata[col];
break;
}
default:
length= ~(uint32) 0;
}
return length;
}
PSI_memory_key key_memory_table_def_memory;
uint table_def::field_metadata_length(uint binlog_type)
{
switch (static_cast<enum_field_types>(binlog_type)) {
case MYSQL_TYPE_TINY_BLOB:
case MYSQL_TYPE_BLOB:
case MYSQL_TYPE_BLOB_COMPRESSED:
case MYSQL_TYPE_MEDIUM_BLOB:
case MYSQL_TYPE_LONG_BLOB:
case MYSQL_TYPE_DOUBLE:
case MYSQL_TYPE_FLOAT:
case MYSQL_TYPE_GEOMETRY:
case MYSQL_TYPE_TIME2:
case MYSQL_TYPE_DATETIME2:
case MYSQL_TYPE_TIMESTAMP2:
return 1;
case MYSQL_TYPE_SET:
case MYSQL_TYPE_ENUM:
case MYSQL_TYPE_STRING:
case MYSQL_TYPE_BIT:
case MYSQL_TYPE_VARCHAR:
case MYSQL_TYPE_VARCHAR_COMPRESSED:
case MYSQL_TYPE_NEWDECIMAL:
return 2;
default:
return 0;
}
}
table_def::table_def(unsigned char *types, ulong size,
uchar *field_metadata, int metadata_size,
uchar *null_bitmap, uint16 flags)
: m_size(size), m_type(0), m_field_metadata_size(metadata_size),
m_field_metadata(0), m_null_bits(0), m_flags(flags),
m_memory(NULL)
{
m_memory= (uchar *)my_multi_malloc(key_memory_table_def_memory, MYF(MY_WME),
&m_type, size,
&m_field_metadata,
size * sizeof(uint16),
&m_null_bits, (size + 7) / 8,
NULL);
bzero(m_field_metadata, size * sizeof(uint16));
if (m_type)
memcpy(m_type, types, size);
else
m_size= 0;
/*
Extract the data from the table map into the field metadata array
iff there is field metadata. The variable metadata_size will be
0 if we are replicating from an older version server since no field
metadata was written to the table map. This can also happen if
there were no fields in the master that needed extra metadata.
*/
if (m_size && metadata_size)
{
int index= 0;
for (unsigned int i= 0; i < m_size; i++)
{
switch (binlog_type(i)) {
case MYSQL_TYPE_TINY_BLOB:
case MYSQL_TYPE_BLOB:
case MYSQL_TYPE_BLOB_COMPRESSED:
case MYSQL_TYPE_MEDIUM_BLOB:
case MYSQL_TYPE_LONG_BLOB:
case MYSQL_TYPE_DOUBLE:
case MYSQL_TYPE_FLOAT:
case MYSQL_TYPE_GEOMETRY:
{
/*
These types store a single byte.
*/
m_field_metadata[i]= field_metadata[index];
index++;
break;
}
case MYSQL_TYPE_SET:
case MYSQL_TYPE_ENUM:
case MYSQL_TYPE_STRING:
{
uint16 x= field_metadata[index++] << 8U; // real_type
x+= field_metadata[index++]; // pack or field length
m_field_metadata[i]= x;
break;
}
case MYSQL_TYPE_BIT:
{
uint16 x= field_metadata[index++];
x = x + (field_metadata[index++] << 8U);
m_field_metadata[i]= x;
break;
}
case MYSQL_TYPE_VARCHAR:
case MYSQL_TYPE_VARCHAR_COMPRESSED:
{
/*
These types store two bytes.
*/
char *ptr= (char *)&field_metadata[index];
m_field_metadata[i]= uint2korr(ptr);
index= index + 2;
break;
}
case MYSQL_TYPE_NEWDECIMAL:
{
uint16 x= field_metadata[index++] << 8U; // precision
x+= field_metadata[index++]; // decimals
m_field_metadata[i]= x;
break;
}
case MYSQL_TYPE_TIME2:
case MYSQL_TYPE_DATETIME2:
case MYSQL_TYPE_TIMESTAMP2:
m_field_metadata[i]= field_metadata[index++];
break;
default:
m_field_metadata[i]= 0;
break;
}
}
}
if (m_size && null_bitmap)
memcpy(m_null_bits, null_bitmap, (m_size + 7) / 8);
}
table_def::~table_def()
{
my_free(m_memory);
#ifndef DBUG_OFF
m_type= 0;
m_size= 0;
#endif
}
/**
@param even_buf point to the buffer containing serialized event
@param event_len length of the event accounting possible checksum alg
@return TRUE if test fails
FALSE as success
@notes
event_buf will have same values on return. However during the process of
caluclating the checksum, it's temporary changed. Because of this the
event_buf argument is not a pointer to const.
*/
bool event_checksum_test(uchar *event_buf, ulong event_len,
enum enum_binlog_checksum_alg alg)
{
bool res= FALSE;
uint16 flags= 0; // to store in FD's buffer flags orig value
if (alg != BINLOG_CHECKSUM_ALG_OFF && alg != BINLOG_CHECKSUM_ALG_UNDEF)
{
ha_checksum incoming;
ha_checksum computed;
if (event_buf[EVENT_TYPE_OFFSET] == FORMAT_DESCRIPTION_EVENT)
{
#ifdef DBUG_ASSERT_EXISTS
int8 fd_alg= event_buf[event_len - BINLOG_CHECKSUM_LEN -
BINLOG_CHECKSUM_ALG_DESC_LEN];
#endif
/*
FD event is checksummed and therefore verified w/o the binlog-in-use flag
*/
flags= uint2korr(event_buf + FLAGS_OFFSET);
if (flags & LOG_EVENT_BINLOG_IN_USE_F)
event_buf[FLAGS_OFFSET] &= ~LOG_EVENT_BINLOG_IN_USE_F;
/*
The only algorithm currently is CRC32. Zero indicates
the binlog file is checksum-free *except* the FD-event.
*/
DBUG_ASSERT(fd_alg == BINLOG_CHECKSUM_ALG_CRC32 || fd_alg == 0);
DBUG_ASSERT(alg == BINLOG_CHECKSUM_ALG_CRC32);
/*
Complile time guard to watch over the max number of alg
*/
compile_time_assert(BINLOG_CHECKSUM_ALG_ENUM_END <= 0x80);
}
incoming= uint4korr(event_buf + event_len - BINLOG_CHECKSUM_LEN);
/* checksum the event content without the checksum part itself */
computed= my_checksum(0, event_buf, event_len - BINLOG_CHECKSUM_LEN);
if (flags != 0)
{
/* restoring the orig value of flags of FD */
DBUG_ASSERT(event_buf[EVENT_TYPE_OFFSET] == FORMAT_DESCRIPTION_EVENT);
event_buf[FLAGS_OFFSET]= (uchar) flags;
}
res= (DBUG_IF("simulate_checksum_test_failure") || computed != incoming);
}
return res;
}
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