On Tue, Jun 25, 2019 at 03:49:33PM -0700, Josh Hunt wrote:
> On 6/25/19 3:18 PM, Greg KH wrote:
> > On Tue, Jun 25, 2019 at 01:29:35PM -0700, Josh Hunt wrote:
> > > On 6/25/19 1:26 PM, Sasha Levin wrote:
> > > > On Tue, Jun 25, 2019 at 01:19:37PM -0400, Josh Hunt wrote:
> > > > > Backport of dad3a9314ac95dedc007bc7dacacb396ea10e376:
> > > >
> > > > You probably meant b6653b3629e5b88202be3c9abc44713973f5c4b4 here.
> > >
> > > I wasn't sure if I should reference the upstream commit or stable commit.
> >
> > The upstream commit please.
>
> Thanks. I'll fix for next version.
>
> >
> > > dad3a9314 is the version of the commit from linux-4.14.y. There may be a
> > > similar issue with the Fixes tag below since that also references the 4.14
> > > vers of the change.
> > >
> > > >
> > > > > tcp_fragment() might be called for skbs in the write queue.
> > > > >
> > > > > Memory limits might have been exceeded because tcp_sendmsg() only
> > > > > checks limits at full skb (64KB) boundaries.
> > > > >
> > > > > Therefore, we need to make sure tcp_fragment() wont punish applications
> > > > > that might have setup very low SO_SNDBUF values.
> > > > >
> > > > > Backport notes:
> > > > > Initial version used tcp_queue type which is not present in older
> > > > > kernels,
> > > > > so added a new arg to tcp_fragment() to determine whether this is a
> > > > > retransmit or not.
> > > > >
> > > > > Fixes: 9daf226ff926 ("tcp: tcp_fragment() should apply sane memory
> > > > > limits")
> > > > > Signed-off-by: Josh Hunt <johunt@xxxxxxxxxx>
> > > > > Reviewed-by: Jason Baron <jbaron@xxxxxxxxxx>
> > > > > ---
> > > > >
> > > > > Eric/Greg - This applies on top of v4.14.130. I did not see anything come
> > > > > through for the older (<4.19) stable kernels yet. Without this change
> > > > > Christoph Paasch's packetrill script (https://lore.kernel.org/netdev/CALMXkpYVRxgeqarp4gnmX7GqYh1sWOAt6UaRFqYBOaaNFfZ5sw@xxxxxxxxxxxxxx/)
> > > > >
> > > > > will fail on 4.14 stable kernels, but passes with this change.
> > > >
> > > > Eric, it would be great if you could Ack this, it's very different from
> > > > your original patch.
> > >
> > > Yes, that would be great.
> >
> > I would prefer if this looks a bit more like the upstream fix, perhaps a
> > backport of the function that added the "direction" of the packet first,
> > and then Eric's patch? As it is, this patch adds a different parameter
> > to the function than what is in Linus's tree, and I bet will cause
> > problems at some later point in time.
>
> The commit which introduced the fn arguments is part of a much larger change
> that created a separate rb-tree for the retransmit queue:
>
> commit 75c119afe14f74b4dd967d75ed9f57ab6c0ef045
> Author: Eric Dumazet <edumazet@xxxxxxxxxx>
> Date: Thu Oct 5 22:21:27 2017 -0700
>
> tcp: implement rb-tree based retransmit queue
>
> I can backport the portion of this change which basically does this:
>
> +enum tcp_queue {
> + TCP_FRAG_IN_WRITE_QUEUE,
> + TCP_FRAG_IN_RTX_QUEUE,
> +};
> +int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
> + struct sk_buff *skb, u32 len,
> + unsigned int mss_now, gfp_t gfp);
>
> and the corresponding call-sites of tcp_fragment(). If we do that then
> Eric's fix (b6653b3629e5b88202be3c9abc44713973f5c4b4) should apply cleanly
> on top of linux-4.14.y. I'm happy to do that if you'd rather go that route.
Yes, that is what I was thinking of, thanks. You expressed it much
better than I could have before my morning coffee :)
> If you want the full rb-tree change into 4.14 then I would defer that to
> Eric, but would argue that IMHO is probably too invasive of a change for a
> LTS kernel.
No, I don't think we should do that work for 4.14.
Also, your change would be suitable for backporting to the older stable
kernels that also need this (4.9.y and 4.4.y.)
thanks,
greg k-h
