netdev - Re: [PATCH net v2] vlan: consolidate VLAN parsing code and limit max parsing depth

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Date:   Tue, 07 Jul 2020 15:49:10 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     toke@...hat.com
Cc:     netdev@...r.kernel.org, cake@...ts.bufferbloat.net,
        dcaratti@...hat.com, jiri@...nulli.us, jhs@...atatu.com,
        xiyou.wangcong@...il.com, toshiaki.makita1@...il.com,
        daniel@...earbox.net
Subject: Re: [PATCH net v2] vlan: consolidate VLAN parsing code and limit
 max parsing depth

From: Toke Høiland-Jørgensen <toke@...hat.com>
Date: Tue,  7 Jul 2020 13:03:25 +0200

> Toshiaki pointed out that we now have two very similar functions to extract
> the L3 protocol number in the presence of VLAN tags. And Daniel pointed out
> that the unbounded parsing loop makes it possible for maliciously crafted
> packets to loop through potentially hundreds of tags.
> 
> Fix both of these issues by consolidating the two parsing functions and
> limiting the VLAN tag parsing to a max depth of 8 tags. As part of this,
> switch over __vlan_get_protocol() to use skb_header_pointer() instead of
> pskb_may_pull(), to avoid the possible side effects of the latter and keep
> the skb pointer 'const' through all the parsing functions.
> 
> v2:
> - Use limit of 8 tags instead of 32 (matching XMIT_RECURSION_LIMIT)
> 
> Reported-by: Toshiaki Makita <toshiaki.makita1@...il.com>
> Reported-by: Daniel Borkmann <daniel@...earbox.net>
> Fixes: d7bf2ebebc2b ("sched: consistently handle layer3 header accesses in the presence of VLANs")
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>

Applied, thank you.