From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet Date: Fri, 12 Apr 2013 15:24:06 +0100 Message-ID: <1365776646-10796-8-git-send-email-wei.liu2@citrix.com> References: <1365776646-10796-1-git-send-email-wei.liu2@citrix.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , , , , , , Wei Liu To: , Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:44209 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752629Ab3DLOYY (ORCPT ); Fri, 12 Apr 2013 10:24:24 -0400 In-Reply-To: <1365776646-10796-1-git-send-email-wei.liu2@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: Some frontend drivers are sending packets > 64 KiB in length. This length overflows the length field in the first slot making the following slots have an invalid length. Turn this error back into a non-fatal error by dropping the packet. To avoid having the following slots having fatal errors, consume all slots in the packet. This does not reopen the security hole in XSA-39 as if the packet as an invalid number of slots it will still hit fatal error case. Signed-off-by: David Vrabel Signed-off-by: Wei Liu --- drivers/net/xen-netback/netback.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 00ae841..e21c15e 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -993,12 +993,22 @@ static int netbk_count_requests(struct xenvif *vif, memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots), sizeof(*txp)); - if (txp->size > first->size) { - netdev_err(vif->dev, - "Invalid tx request, slot size %u > remaining size %u\n", - txp->size, first->size); - netbk_fatal_tx_err(vif); - return -EIO; + + /* If the guest submitted a frame >= 64 KiB then + * first->size overflowed and following slots will + * appear to be larger than the frame. + * + * This cannot be fatal error as there are buggy + * frontends that do this. + * + * Consume all slots and drop the packet. + */ + if (!drop_err && txp->size > first->size) { + if (net_ratelimit()) + netdev_dbg(vif->dev, + "Invalid tx request, slot size %u > remaining size %u\n", + txp->size, first->size); + drop_err = -EIO; } first->size -= txp->size; -- 1.7.10.4