Description:- mysqlslap is a diagnostic utility designed to
emulate client load for a MySQL server and to report the
timing of each stage. This utility crashes when invalid
values are passed to the options 'num_int_cols_opt' or
'num_chars_cols_opt' or 'engine'.

Analysis:- mysqlslap uses "parse_option()" to parse the
values specified to the options 'num_int_cols_opt',
'num_chars_cols_opt' and 'engine'. These options takes
values separated by commas. In "parse_option()", the comma
separated values are separated and copied into a buffer
without checking the length of the string to be copied. The
size of the buffer is defined by a macro HUGE_STRING_LENGTH
whose value is 8196. So if the length of the any of the
comma separated value exceeds HUGE_STRING_LENGTH, will
result in a buffer overflow.

Fix:- A check is introduced in "parse_option()" to check
whether the size of the string to be copied is more than
HUGE_STRING_LENGTH. If it is more, an error, "Invalid value
specified for the option 'xxx'" is thrown.
Option length was incorrectly calculated for the last comma
separated value. So fixed that as well.