netdev - Re: [PATCH stable 4.4 0/9] fix SegmentSmack in stable branch (CVE-2018-5390)

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Date:   Thu, 16 Aug 2018 09:44:57 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     maowenan <maowenan@...wei.com>
Cc:     dwmw2@...radead.org, gregkh@...ux-foundation.org,
        netdev@...r.kernel.org, eric.dumazet@...il.com,
        edumazet@...gle.com, davem@...emloft.net, ycheng@...gle.com,
        jdw@...zon.de, stable@...r.kernel.org, Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH stable 4.4 0/9] fix SegmentSmack in stable branch
 (CVE-2018-5390)

On Thu, Aug 16, 2018 at 03:39:14PM +0800, maowenan wrote:
> 
> 
> On 2018/8/16 15:23, Michal Kubecek wrote:
> > On Thu, Aug 16, 2018 at 03:19:12PM +0800, maowenan wrote:
> >> On 2018/8/16 14:52, Michal Kubecek wrote:
> >>>
> >>> My point is that backporting all this into stable 4.4 is quite intrusive
> >>> so that if we can achieve similar results with a simple fix of an
> >>> obvious omission, it would be preferrable.
> >>
> >> There are five patches in mainline to fix this CVE, only two patches
> >> have no effect on stable 4.4, the important reason is 4.4 use simple
> >> queue but mainline use RB tree.
> >>
> >> I have tried my best to use easy way to fix this with dropping packets
> >> 12.5%(or other value) based on simple queue, but the result is not
> >> very well, so the RB tree is needed and tested result is my desire.
> >>
> >> If we only back port two patches but they don't fix the issue, I think
> >> they don't make any sense.
> > 
> > There is an obvious omission in one of the two patches and Takashi's
> > patch fixes it. If his follow-up fix (applied on top of what is in
> > stable 4.4 now) addresses the problem, I would certainly prefer using it
> > over backporting the whole series.
> 
> Do you mean below codes from Takashi can fix this CVE?
> But I have already tested like this two days ago, it is not good effect.

IIRC what you proposed was different, you proposed to replace the "=" in
the other branch by "+=".

Michal Kubecek


> 
> Could you try to test with POC programme mentioned previous mail in case I made mistake?
> 
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 4a261e078082..9c4c6cd0316e 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -4835,6 +4835,7 @@ static void tcp_collapse_ofo_queue(struct sock *sk)
>  			end = TCP_SKB_CB(skb)->end_seq;
>  			range_truesize = skb->truesize;
>  		} else {
> +			range_truesize += skb->truesize;
>  			if (before(TCP_SKB_CB(skb)->seq, start))
>  				start = TCP_SKB_CB(skb)->seq;
>  			if (after(TCP_SKB_CB(skb)->end_seq, end))
> -- 
> 
> 
> > 
> > Michal Kubecek
> > 
> > 
> > .
> > 
>