From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH net 3/3] xen-netback: BUG_ON in xenvif_rx_action() not catching overflow Date: Thu, 27 Mar 2014 12:28:26 +0000 Message-ID: <1395923306.22909.107.camel@kazak.uk.xensource.com> References: <1395922988-37702-1-git-send-email-paul.durrant@citrix.com> <1395922988-37702-4-git-send-email-paul.durrant@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: , , Wei Liu , Sander Eikelenboom To: Paul Durrant Return-path: Received: from smtp.citrix.com ([66.165.176.89]:44228 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752124AbaC0M2o (ORCPT ); Thu, 27 Mar 2014 08:28:44 -0400 In-Reply-To: <1395922988-37702-4-git-send-email-paul.durrant@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2014-03-27 at 12:23 +0000, Paul Durrant wrote: > The BUG_ON to catch ring overflow in xenvif_rx_action() makes the assumption > that meta_slots_used == ring slots used. This is not the case for GSO > packets. Can you explain why not here please. > This patch changes the test to actually check ring slots. > > Signed-off-by: Paul Durrant > Cc: Ian Campbell > Cc: Wei Liu > Cc: Sander Eikelenboom > --- > drivers/net/xen-netback/netback.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > index ac35489..ae7351f 100644 > --- a/drivers/net/xen-netback/netback.c > +++ b/drivers/net/xen-netback/netback.c > @@ -481,6 +481,8 @@ static void xenvif_rx_action(struct xenvif *vif) > > while ((skb = skb_dequeue(&vif->rx_queue)) != NULL) { > RING_IDX max_slots_needed; > + RING_IDX old_req_cons; > + RING_IDX ring_slots_used; > int i; > > /* We need a cheap worse case estimate for the number of > @@ -520,8 +522,12 @@ static void xenvif_rx_action(struct xenvif *vif) > vif->rx_last_skb_slots = 0; > > sco = (struct skb_cb_overlay *)skb->cb; > + > + old_req_cons = vif->rx.req_cons; > sco->meta_slots_used = xenvif_gop_skb(skb, &npo); > - BUG_ON(sco->meta_slots_used > max_slots_needed); > + ring_slots_used = vif->rx.req_cons - old_req_cons; > + > + BUG_ON(ring_slots_used > max_slots_needed); > > __skb_queue_tail(&rxq, skb); > }