netdev - Re: [syzbot] KASAN: use-after-free Read in nf

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Message-ID: <20220517194751.GA4316@breakpoint.cc>
Date:   Tue, 17 May 2022 21:47:51 +0200
From:   Florian Westphal <fw@...len.de>
To:     syzbot <syzbot+793a590957d9c1b96620@...kaller.appspotmail.com>
Cc:     ali.abdallah@...e.com, coreteam@...filter.org, davem@...emloft.net,
        edumazet@...gle.com, fw@...len.de, kadlec@...filter.org,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        ozsh@...dia.com, pabeni@...hat.com, pablo@...filter.org,
        paulb@...dia.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Read in nf_confirm

syzbot <syzbot+793a590957d9c1b96620@...kaller.appspotmail.com> wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    d887ae3247e0 octeontx2-pf: Remove unnecessary synchronize_..
> git tree:       net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=17f2b659f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b1aab282dc5dd920
> dashboard link: https://syzkaller.appspot.com/bug?extid=793a590957d9c1b96620
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1313dce6f00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=169eb59ef00000
> 
> The issue was bisected to:
> 
> commit 1397af5bfd7d32b0cf2adb70a78c9a9e8f11d912
> Author: Florian Westphal <fw@...len.de>
> Date:   Mon Apr 11 11:01:18 2022 +0000
> 
>     netfilter: conntrack: remove the percpu dying list

AFAICS this bug exists since
Fixes: 71d8c47fc653 ("netfilter: conntrack: introduce clash resolution on insertion race")

nf_confirm needs to re-fetch 'ct' from skb->_nfct.  Will send a patch.