grow_ary() should not copy struct ipc_id_ary (it copies new->p, not 
new). Due to this, memcpy() src pointer could hit unmapped vmalloc page 
when near page boundary.

Found during OpenVZ stress testing

Signed-Off-By: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-Off-By: Kirill Korotaev <dev@openvz.org>