netdev - Re: [Patch net] net_sched: refetch skb protocol for each filter

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Message-ID: <7d4c774c-c17d-1739-81f3-bdab67099138@mojatatu.com>
Date:   Wed, 16 Jan 2019 08:59:08 -0500
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     Martin Olsson <martin.olsson+netdev@...torsecurity.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [Patch net] net_sched: refetch skb protocol for each filter

On 2019-01-11 9:55 p.m., Cong Wang wrote:
> Martin reported a set of filters don't work after changing
> from reclassify to continue. Looking into the code, it
> looks like skb protocol is not always fetched for each
> iteration of the filters. But, as demonstrated by Martin,
> TC actions could modify skb->protocol, for example act_vlan,
> this means we have to refetch skb protocol in each iteration,
> rather than using the one we fetch in the beginning of the loop.
> 
> This bug is _not_ introduced by commit 3b3ae880266d
> ("net: sched: consolidate tc_classify{,_compat}"), technically,
> if act_vlan is the only action that modifies skb protocol, then
> it is commit c7e2b9689ef8 ("sched: introduce vlan action") which
> introduced this bug.
> 
> Reported-by: Martin Olsson <martin.olsson+netdev@...torsecurity.com>
> Cc: Jamal Hadi Salim <jhs@...atatu.com>
> Cc: Jiri Pirko <jiri@...nulli.us>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Acked-by: Jamal Hadi Salim <jhs@...atatu.com>

cheers,
jamal