netdev - Re: [PATCH net] net/sched: act_ct: fix skb leak and crash on ooo frags

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Date: Wed, 3 Jan 2024 17:49:31 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: vladbu@...dia.com, Xin Long <lucien.xin@...il.com>
Cc: Tao Liu <taoliu828@....com>, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, paulb@...dia.com, netdev@...r.kernel.org,
 simon.horman@...igine.com, xiyou.wangcong@...il.com, pablo@...filter.org
Subject: Re: [PATCH net] net/sched: act_ct: fix skb leak and crash on ooo
 frags

On Thu, 28 Dec 2023 16:14:57 +0800 Tao Liu wrote:
> act_ct adds skb->users before defragmentation. If frags arrive in order,
> the last frag's reference is reset in:
> 
>   inet_frag_reasm_prepare
>     skb_morph
> 
> which is not straightforward.
> 
> However when frags arrive out of order, nobody unref the last frag, and
> all frags are leaked. The situation is even worse, as initiating packet
> capture can lead to a crash[0] when skb has been cloned and shared at the
> same time.
> 
> Fix the issue by removing skb_get() before defragmentation. act_ct
> returns TC_ACT_CONSUMED when defrag failed or in progress.

Vlad, Xin Long, does this look good to you?
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