netdev - Re: [PATCH v3 net-next 1/2] net: skbuff: Remove errornous length validation in skb_vlan

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20160922.013629.367187899272461834.davem@davemloft.net>
Date:   Thu, 22 Sep 2016 01:36:29 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     shmulik.ladkani@...ellosystems.com
Cc:     jiri@...lanox.com, daniel@...earbox.net, pshelar@....org,
        eric.dumazet@...il.com, netdev@...r.kernel.org,
        shmulik.ladkani@...il.com
Subject: Re: [PATCH v3 net-next 1/2] net: skbuff: Remove errornous length
 validation in skb_vlan_pop()

From: Shmulik Ladkani <shmulik.ladkani@...ellosystems.com>
Date: Tue, 20 Sep 2016 12:48:36 +0300

> In 93515d53b1
>   "net: move vlan pop/push functions into common code"
> skb_vlan_pop was moved from its private location in openvswitch to
> skbuff common code.
> 
> In case skb has non hw-accel vlan tag, the original 'pop_vlan()' assured
> that skb->len is sufficient (if skb->len < VLAN_ETH_HLEN then pop was
> considered a no-op).
> 
> This validation was moved as is into the new common 'skb_vlan_pop'.
> 
> Alas, in its original location (openvswitch), there was a guarantee that
> 'data' points to the mac_header, therefore the 'skb->len < VLAN_ETH_HLEN'
> condition made sense.
> However there's no such guarantee in the generic 'skb_vlan_pop'.
> 
> For short packets received in rx path going through 'skb_vlan_pop',
> this causes 'skb_vlan_pop' to fail pop-ing a valid vlan hdr (in the non
> hw-accel case) or to fail moving next tag into hw-accel tag.
> 
> Remove the 'skb->len < VLAN_ETH_HLEN' condition entirely:
> It is superfluous since inner '__skb_vlan_pop' already verifies there
> are VLAN_ETH_HLEN writable bytes at the mac_header.
> 
> Note this presents a slight change to skb_vlan_pop() users:
> In case total length is smaller than VLAN_ETH_HLEN, skb_vlan_pop() now
> returns an error, as opposed to previous "no-op" behavior.
> Existing callers (e.g. tc act vlan, ovs) usually drop the packet if
> 'skb_vlan_pop' fails.
> 
> Fixes: 93515d53b1 ("net: move vlan pop/push functions into common code")
> Signed-off-by: Shmulik Ladkani <shmulik.ladkani@...il.com>

Applied.