Recommit to 5.1.22.
Killing a SELECT query with KILL QUERY or KILL CONNECTION
causes a server crash if the query cache is enabled.

Normal evaluation of a query may be interrupted by the
KILL QUERY/CONNECTION statement, in this case the mysql_execute_command
function returns TRUE, and the thd->killed flag has true value.
In this case the result of the query may
be cached incompletely (omitting call to query_cache_insert inside
the net_real_write function), and next call to query_cache_end_of_result
may lead to server crash.
Thus, the query_cache_end_of_result function has been modified to abort
query cache in the case of killed thread.



sql/sql_cache.cc:
  Fixed bug #30201.
  Recommit to 5.1.22.
  The  query_cache_end_of_result function has been modified to abort query
  cache in the case of query execution failure. Also this function has been
  modified to remove incomplete query block.