Pull up following revision(s) (requested by maxv in ticket #1902):
	src/sys/compat/linux/common/linux_exec_elf32.c	1.91 via patch

A specially-crafted binary could easily control a kernel array index.
Add some checks to ensure that nothing will be read outside the allocated
area. Rewrite the code so that we don't need to allocate the whole section.

Spotted by several developers, patch from chs@/enami@
Ticket 1902.
Ticket 1905.