From: Daniel Borkmann <daniel@iogearbox•net>
To: Shmulik Ladkani <shmulik.ladkani@gmail•com>,
pravin shelar <pshelar@ovn•org>
Cc: Jiri Pirko <jiri@mellanox•com>,
"David S . Miller" <davem@davemloft•net>,
Linux Kernel Network Developers <netdev@vger•kernel.org>
Subject: Re: [PATCH] net: skbuff: Fix length validation in skb_vlan_pop()
Date: Mon, 19 Sep 2016 14:22:57 +0200 [thread overview]
Message-ID: <57DFD8A1.1090103@iogearbox.net> (raw)
In-Reply-To: <20160919091538.56defd2b@pixies>
On 09/19/2016 08:15 AM, Shmulik Ladkani wrote:
> On Sun, 18 Sep 2016 13:26:30 -0700, pshelar@ovn•org wrote:
>> On Sun, Sep 18, 2016 at 3:09 AM, Shmulik Ladkani
>> <shmulik.ladkani@gmail•com> wrote:
>>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>>> index 1e329d4112..cc2c004838 100644
>>> --- a/net/core/skbuff.c
>>> +++ b/net/core/skbuff.c
>>> @@ -4537,7 +4537,7 @@ int skb_vlan_pop(struct sk_buff *skb)
>>> } else {
>>> if (unlikely((skb->protocol != htons(ETH_P_8021Q) &&
>>> skb->protocol != htons(ETH_P_8021AD)) ||
>>> - skb->len < VLAN_ETH_HLEN))
>>> + skb->mac_len < VLAN_ETH_HLEN))
>>
>> There is already check in __skb_vlan_pop() to validate skb for a vlan
>> header. So it is safe to drop this check entirely.
>
> Seems validation in '__skb_vlan_pop' has slightly different semantics:
>
> unsigned int offset = skb->data - skb_mac_header(skb);
>
> __skb_push(skb, offset);
> err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
>
> this pushes 'data' back to mac_header, then makes sure there's sufficient
> place in skb to _store_ VLAN_ETH_HLEN bytes (by pulling into linear part
> if needed, or erroring if skb is too small).
Yes, but this skb_ensure_writable() is needed for doing the memmove anyway.
> There's no guarantee the original mac header was sized VLAN_ETH_HLEN.
I'm wondering, what happens when you'd call this on tx path, when you'd
change that to suggested skb->mac_len? Isn't that 0 in such case, thus
such setups could fail then?
next prev parent reply other threads:[~2016-09-19 12:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-18 10:09 [PATCH] net: skbuff: Fix length validation in skb_vlan_pop() Shmulik Ladkani
2016-09-18 20:26 ` pravin shelar
2016-09-19 6:15 ` Shmulik Ladkani
2016-09-19 12:22 ` Daniel Borkmann [this message]
2016-09-19 13:05 ` Shmulik Ladkani
2016-09-19 15:20 ` Shmulik Ladkani
2016-09-19 20:04 ` Shmulik Ladkani
2016-09-19 20:46 ` pravin shelar
2016-09-20 4:36 ` Shmulik Ladkani
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=57DFD8A1.1090103@iogearbox.net \
--to=daniel@iogearbox$(echo .)net \
--cc=davem@davemloft$(echo .)net \
--cc=jiri@mellanox$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=pshelar@ovn$(echo .)org \
--cc=shmulik.ladkani@gmail$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox