staging: r8712u: fix bug in r8712_recv_indicatepkt()

64bit arches have a buggy r8712u driver, let's fix it.

skb->tail must be set properly or network stack behavior is undefined.

Addresses https://bugzilla.redhat.com/show_bug.cgi?id=847525
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=45071

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Dave Jones <davej@redhat.com>
Cc: stable <stable@vger.kernel.org> [2.6.37+]
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/recv_linux.c

@@ -117,13 +117,8 @@ void r8712_recv_indicatepkt(struct _adapter *padapter,
 	if (skb == NULL)
 		goto _recv_indicatepkt_drop;
 	skb->data = precv_frame->u.hdr.rx_data;
-#ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->tail = (sk_buff_data_t)(precv_frame->u.hdr.rx_tail -
-		     precv_frame->u.hdr.rx_head);
-#else
-	skb->tail = (sk_buff_data_t)precv_frame->u.hdr.rx_tail;
-#endif
 	skb->len = precv_frame->u.hdr.len;
+	skb_set_tail_pointer(skb, skb->len);
 	if ((pattrib->tcpchk_valid == 1) && (pattrib->tcp_chkrpt == 1))
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	else