If we allocate less than sizeof(struct attrlist) then we end up
corrupting memory or doing a ZERO_PTR_SIZE dereference.

This can only be triggered with CAP_SYS_ADMIN.
Reported-by: NNico Golde <nico@ngolde.de>
Reported-by: NFabian Yamaguchi <fabs@goesec.de>
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>