netdev - Re: [PATCH v3 net,stable] tun: fix vlan packet truncation

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Message-Id: <20180418.135257.362879449353986102.davem@davemloft.net>
Date:   Wed, 18 Apr 2018 13:52:57 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     bjorn@...k.no
Cc:     netdev@...r.kernel.org, jasowang@...hat.com
Subject: Re: [PATCH v3 net,stable] tun: fix vlan packet truncation

From: Bjørn Mork <bjorn@...k.no>
Date: Tue, 17 Apr 2018 22:46:38 +0200

> Bogus trimming in tun_net_xmit() causes truncated vlan packets.
> 
> skb->len is correct whether or not skb_vlan_tag_present() is true. There
> is no more reason to adjust the skb length on xmit in this driver than
> any other driver. tun_put_user() adds 4 bytes to the total for tagged
> packets because it transmits the tag inline to userspace.  This is
> similar to a nic transmitting the tag inline on the wire.
> 
> Reproducing the bug by sending any tagged packet through back-to-back
> connected tap interfaces:
 ...
> Fixes: aff3d70a07ff ("tun: allow to attach ebpf socket filter")
> Cc: Jason Wang <jasowang@...hat.com>
> Signed-off-by: Bjørn Mork <bjorn@...k.no>

Applied and queued up for -stable, thanks.