netdev - Re: [PATCH net] net: Handle negative checksum offset in skb-checksum-help

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] [day] [month] [year] [list]

Date:	Mon, 21 Sep 2015 21:44:03 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net] net: Handle negative checksum offset in skb-checksum-help

On Mon, Sep 21, 2015 at 8:21 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Mon, 2015-09-21 at 19:49 -0700, Pravin Shelar wrote:
>> On Mon, Sep 21, 2015 at 7:14 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> > On Mon, 2015-09-21 at 18:04 -0700, Pravin Shelar wrote:
>> >> On Mon, Sep 21, 2015 at 5:14 PM, David Miller <davem@...emloft.net> wrote:
>> >> > From: Pravin B Shelar <pshelar@...ira.com>
>> >> > Date: Sun, 20 Sep 2015 23:53:17 -0700
>> >> >
>> >> >> VXLAN device can receive skb with checksum partial. But the checksum
>> >> >> offset could be in outer header which is pulled on receive.
>> >> >
>> >> > Such a scenerio is a bug.
>> >> >
>> >> > Anything that pulls off a header should use a utility function such
>> >> > as skb_pull_rcsum() or skb_postpull_rcsum() to make sure this gets
>> >> > fixed up properly.
>> >>
>> >> skb_postpull_rcsum() does not change checksum-offset. vxlan receive
>> >> already calls this function.
>> >
>> > Then the bug is here.
>> >
>> > Otherwise we might have to 'fix' other places.
>> >
>> I posted a patch to fix skb_postpull_rcsum() to handle this case. But
>> that was not accepted.
>> https://patchwork.ozlabs.org/patch/512625/
>>
>> And specific solution for skb_checksum_help() was suggested.
>>
>> http://marc.info/?l=linux-netdev&m=144108078931774&w=2
>
> If we pull a header where the csum is, then for sure CHECKSUM_PARTIAL
> becomes buggy and void.
>
> Tom was not advocating doing an operation (skb_postpull_rcsum()) leaving
> skb in a wrong state.
>
> We should fix callers that are pulling header in such a way.
>

So same as first patch but set skb checksum flag to CHECKSUM_NONE?
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html