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

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Date:   Mon, 8 Apr 2019 08:49:52 -0600
From:   Captain Wiggum <captwiggum@...il.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     davem@...emloft.net,
        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

Hi Sasha,

This patch cannot be applied to upstream, the code is significantly different.
Therefore, this un-do patch would not be seen in the upstream git log.
It was solved there by coding a better solution, not by the un-do patch.

Please consider this:
Upstream passes the TAHI IPv6 protocol tests. All the LTS kernels do NOT.
This is the patch that causes the failure in 4.9, 4.14, 4.19 LTS kernels.

And this patch has been in place with 4.9.134, a long time.
It is not right that "Linux" can not pass the IPv6 protocol test.
My executive are asking me why "Linux" is not fit for IPv6 deployments.

--John Masinter

On Sat, Apr 6, 2019 at 8:15 AM Sasha Levin <sashal@...nel.org> wrote:
>
> 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