Bug #18463911 : SERVER CRASHES ON CREATING A TEMP TABLE

                WITH CERTAIN MAX_HEAP_TABLE_SIZE VALUES

Description:
When the  system variable 'max_heap_table_size'
is set to 20GB, the server crashes on creation of a
temporary tables or tables using MEMORY storage engine.

Analysis:
The variable 'max_record' determines the amount heap
allocated for the records of the table. This value
is determined using the 'max_heap_table_size' variable.
'records_in_block' in turn uses the max_records to
determine the number of records per block.

When the 'max_heap_table_size' is set to 20GB, then
the 'records_in_block' is calculated to a value of
2^28.

The size of the block determined by multiplying the
'records_in_block' and 'recbuffer' results in overflow
and hence the value becomes zero. As a result, zero bytes
of the heap is allocated for the table. This will
result in a server crash when the table is accessed.

Fix:
The variables 'records_in_block' and 'recbuffer' are
typecasted to 'unsigned long' while calculating the
size of the block.

0 files changed, 0 insertions, 0 deletions