netdev - Re: [PATCH v2 net] xen-netback: make sure that hashes are not send to unaware frontends

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Message-Id: <20161007.235315.1445609703306777270.davem@davemloft.net>
Date:   Fri, 07 Oct 2016 23:53:15 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     paul.durrant@...rix.com
Cc:     netdev@...r.kernel.org, xen-devl@...ts.xenproject.org,
        wei.liu2@...rix.com
Subject: Re: [PATCH v2 net] xen-netback: make sure that hashes are not send
 to unaware frontends

From: Paul Durrant <paul.durrant@...rix.com>
Date: Fri, 7 Oct 2016 09:32:31 +0100

> In the case when a frontend only negotiates a single queue with xen-
> netback it is possible for a skbuff with a s/w hash to result in a
> hash extra_info segment being sent to the frontend even when no hash
> algorithm has been configured. (The ndo_select_queue() entry point makes
> sure the hash is not set if no algorithm is configured, but this entry
> point is not called when there is only a single queue). This can result
> in a frontend that is unable to handle extra_info segments being given
> such a segment, causing it to crash.
> 
> This patch fixes the problem by clearing the hash in ndo_start_xmit()
> instead, which is clearly guaranteed to be called irrespective of the
> number of queues.
> 
> Signed-off-by: Paul Durrant <paul.durrant@...rix.com>

Applied, thanks.