netdev - Re: [PATCH net v2] net: bridge: fix stale eth hdr pointer in br_dev

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Date:   Mon, 24 Feb 2020 11:13:55 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     nikolay@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net v2] net: bridge: fix stale eth hdr pointer in
 br_dev_xmit

From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Date: Mon, 24 Feb 2020 18:46:22 +0200

> In br_dev_xmit() we perform vlan filtering in br_allowed_ingress() but
> if the packet has the vlan header inside (e.g. bridge with disabled
> tx-vlan-offload) then the vlan filtering code will use skb_vlan_untag()
> to extract the vid before filtering which in turn calls pskb_may_pull()
> and we may end up with a stale eth pointer. Moreover the cached eth header
> pointer will generally be wrong after that operation. Remove the eth header
> caching and just use eth_hdr() directly, the compiler does the right thing
> and calculates it only once so we don't lose anything.
> 
> Fixes: 057658cb33fb ("bridge: suppress arp pkts on BR_NEIGH_SUPPRESS ports")
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> ---
> v2: remove syzbot's reported-by tag, this seems to be a different bug

Applied and queued up for -stable, thanks Nikolay.