netdev - Re: [PATCH net] ipv6: un-do: defrag: drop non-last frags smaller than min mtu

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Date:   Sat, 6 Apr 2019 10:15:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Captain Wiggum <captwiggum@...il.com>, davem@...emloft.net
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Florian Westphal <fw@...len.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Peter Oskolkov <posk@...gle.com>, netdev@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH net] ipv6: un-do: defrag: drop non-last frags smaller
 than min mtu

On Fri, Apr 05, 2019 at 10:22:51AM -0600, Captain Wiggum wrote:
>I know it affects 4.9, 4.14, 4.19.
>I have not tested the older LTS kernels.
>But any LTS kernel that previously received this commit is affected:
>...  commit a8444b1ccb20339774af58e40ad42296074fb484
>...  ipv6: defrag: drop non-last frags smaller than min mtu
>
>
>
>On Thu, Apr 4, 2019 at 10:50 PM Greg Kroah-Hartman
><gregkh@...uxfoundation.org> wrote:
>>
>> On Thu, Apr 04, 2019 at 06:18:30PM -0600, Captain Wiggum wrote:
>> > Hi Greg,
>> >
>> > A previous bad patch breaks 18 test cases for IPv6 fragment headers.
>> > This has already been un-done in upstream, but not in any of the LTS.
>> > However two upstream patches are first needed to cover a DoS vulnerability.
>> >
>> > For background, there are two mail threads in [netdev] on this subject:
>> > 1) Subject: TAHI testing fails for IPv6 Fragments in Kernel 4.9 (from
>> > captwiggum)
>> > 2) Subject: Please merge IPv6 fix for drop fragment smaller than MTU
>> > (from captwiggum)
>> >
>> > Two patches from upstream needed first to cover the DoS:
>> >
>> > commit d4289fcc9b16b89619ee1c54f829e05e56de8b9a
>> > net: IP6 defrag: use rbtrees for IPv6 defrag
>> >
>> > commit 997dd96471641e147cb2c33ad54284000d0f5e35
>> > net: IP6 defrag: use rbtrees in nf_conntrack_reasm.c
>> >
>> > One undo-patch to fix the IPv6 fragment headers:
>> >
>> > ipv6: defrag: drop non-last frags smaller than min mtu
>> > UN-DO: commit a8444b1ccb20339774af58e40ad42296074fb484
>>
>> For what kernel version(s) do these patches need to be applied?
>>
>> thanks,
>>
>> greg k-h

I see that 0ed4229b08c1 ("ipv6: defrag: drop non-last frags smaller than
min mtu") wasn't reverted upstream, why is a revert needed on the stable
trees?

David, could you ack these requests?

--
Thanks,
Sasha