get_compat_bpf_fprog(): don't copyin field-by-field

{

	struct compat_sock_fprog __user *fprog32 = (struct compat_sock_fprog __user *)optval;

	struct sock_fprog __user *kfprog = compat_alloc_user_space(sizeof(struct sock_fprog));

	compat_uptr_t ptr;

	u16 len;

	if (!access_ok(VERIFY_READ, fprog32, sizeof(*fprog32)) ||

	    !access_ok(VERIFY_WRITE, kfprog, sizeof(struct sock_fprog)) ||

	    __get_user(len, &fprog32->len) ||

	    __get_user(ptr, &fprog32->filter) ||

	    __put_user(len, &kfprog->len) ||

	    __put_user(compat_ptr(ptr), &kfprog->filter))

	struct compat_sock_fprog f32;

	struct sock_fprog f;

	if (copy_from_user(&f32, fprog32, sizeof(*fprog32)))

		return NULL;

	memset(&f, 0, sizeof(f));

	f.len = f32.len;

	f.filter = compat_ptr(f32.filter);

	if (copy_to_user(kfprog, &f, sizeof(struct sock_fprog)))

		return NULL;

	return kfprog;