linux-kernel - Re: [PATCH v2] netfilter: protect nft_ct_pcpu_template

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Date:   Wed, 11 Aug 2021 11:22:02 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     kadlec@...filter.org, fw@...len.de, davem@...emloft.net,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+649e339fa6658ee623d3@...kaller.appspotmail.com
Subject: Re: [PATCH v2] netfilter: protect nft_ct_pcpu_template_refcnt with
 mutex

On Tue, Aug 10, 2021 at 03:59:20PM +0300, Pavel Skripkin wrote:
> Syzbot hit use-after-free in nf_tables_dump_sets. The problem was in
> missing lock protection for nft_ct_pcpu_template_refcnt.
> 
> Before commit f102d66b335a ("netfilter: nf_tables: use dedicated
> mutex to guard transactions") all transactions were serialized by global
> mutex, but then global mutex was changed to local per netnamespace
> commit_mutex.
> 
> This change causes use-after-free bug, when 2 netnamespaces concurently
> changing nft_ct_pcpu_template_refcnt without proper locking. Fix it by
> adding nft_ct_pcpu_mutex and protect all nft_ct_pcpu_template_refcnt
> changes with it.

Applied to nf.git, thanks