From: Olaf Kirch <okir@suse.de>

Authentication code in net/sunrpc makes frequent use of groups_alloc(0),
which seems to clobber memory past the end of what it allocated.

If called with gidsetsize == 0, groups_alloc will set nblocks = 0,
but still does a

	group_info->blocks[0] = group_info->small_block;