netdev - Re: [PATCH net] net/core: check length before updating Ethertype in skb_mpls

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Message-Id: <20201004.151016.247027928254011553.davem@davemloft.net>
Date:   Sun, 04 Oct 2020 15:10:16 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     gnault@...hat.com
Cc:     kuba@...nel.org, netdev@...r.kernel.org, martin.varghese@...ia.com,
        dcaratti@...hat.com
Subject: Re: [PATCH net] net/core: check length before updating Ethertype
 in skb_mpls_{push,pop}

From: Guillaume Nault <gnault@...hat.com>
Date: Fri, 2 Oct 2020 21:53:08 +0200

> Openvswitch allows to drop a packet's Ethernet header, therefore
> skb_mpls_push() and skb_mpls_pop() might be called with ethernet=true
> and mac_len=0. In that case the pointer passed to skb_mod_eth_type()
> doesn't point to an Ethernet header and the new Ethertype is written at
> unexpected locations.
> 
> Fix this by verifying that mac_len is big enough to contain an Ethernet
> header.
> 
> Fixes: fa4e0f8855fc ("net/sched: fix corrupted L2 header with MPLS 'push' and 'pop' actions")
> Signed-off-by: Guillaume Nault <gnault@...hat.com>

Applied and queued up for -stable, thanks.