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From: Florian Westphal <fw@strlen.de>
To: Pavel Skripkin <paskripkin@gmail.com>
Cc: Florian Westphal <fw@strlen.de>,
	syzbot <syzbot+649e339fa6658ee623d3@syzkaller.appspotmail.com>,
	coreteam@netfilter.org, davem@davemloft.net,
	kadlec@netfilter.org, kuba@kernel.org,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	netfilter-devel@vger.kernel.org, pablo@netfilter.org,
	syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Write in nft_ct_tmpl_put_pcpu
Date: Mon, 9 Aug 2021 23:40:27 +0200	[thread overview]
Message-ID: <20210809214027.GQ607@breakpoint.cc> (raw)
In-Reply-To: <2d002841-402c-2bc3-2b33-3e6d1cd14c23@gmail.com>

Pavel Skripkin <paskripkin@gmail.com> wrote:
> Dumb question: why per_cpu() will return 2 different pointers for CPU 1 and
> CPU 0? As I understand for_each_possible_cpu() will iterate over all
> CPUs which could ever be enabled. So, we can hit situation when 2 concurrent
> processes call per_cpu() with same cpu value (*).

Yes, that is what I was trying to say, the race is that we can have > 1
processes here ever since the global transaction mutex was removed in 2018.

> Anyway, I think, moving locking a bit higher is good here, let's test it. I
> will prepare a patch, if it will pass syzbot testing, thanks!

It looks correct to me, thanks.

  reply	other threads:[~2021-08-09 21:40 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-07 13:44 syzbot
2021-08-07 20:50 ` syzbot
2021-08-09 19:22 ` Pavel Skripkin
2021-08-09 20:39   ` Florian Westphal
2021-08-09 21:16     ` Pavel Skripkin
2021-08-09 21:40       ` Florian Westphal [this message]
2021-08-10  3:18       ` syzbot
2021-08-10  2:59   ` syzbot

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