staging/lustre/llite: fix ll_getname user buffer copy
staging/lustre/llite: fix ll_getname user buffer copy

strncpy_from_user could return negative values on error,
so need to take those into account.
Since ll_getname is used to get a single component name from userspace
to transfer to server as-is, there's no need to allocate 4k buffer
as done by __getname. Allocate NAME_MAX+1 buffer instead to ensure
we have enough for a null terminated max valid length buffer.

This was discovered by Al Viro in https://lkml.org/lkml/2015/4/11/243

Signed-off-by: Oleg Drokin <bc74f4f071a5a33f00ab88a6d6385b5e6638b86c@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs