From: David Miller <davem@davemloft.net>
To: fw@strlen.de
Cc: netdev@vger.kernel.org, cpaasch@apple.com, pabeni@redhat.com
Subject: Re: [PATCH net] mptcp: fix use-after-free on tcp fallback
Date: Wed, 05 Feb 2020 14:08:35 +0100 (CET) [thread overview]
Message-ID: <20200205.140835.1375589051372133185.davem@davemloft.net> (raw)
In-Reply-To: <20200204171230.618-1-fw@strlen.de>
From: Florian Westphal <fw@strlen.de>
Date: Tue, 4 Feb 2020 18:12:30 +0100
> When an mptcp socket connects to a tcp peer or when a middlebox interferes
> with tcp options, mptcp needs to fall back to plain tcp.
> Problem is that mptcp is trying to be too clever in this case:
>
> It attempts to close the mptcp meta sk and transparently replace it with
> the (only) subflow tcp sk.
>
> Unfortunately, this is racy -- the socket is already exposed to userspace.
> Any parallel calls to send/recv/setsockopt etc. can cause use-after-free:
>
> BUG: KASAN: use-after-free in atomic_try_cmpxchg include/asm-generic/atomic-instrumented.h:693 [inline]
...
> While the use-after-free can be resolved, there is another problem:
> sock->ops and sock->sk assignments are not atomic, i.e. we may get calls
> into mptcp functions with sock->sk already pointing at the subflow socket,
> or calls into tcp functions with a mptcp meta sk.
>
> Remove the fallback code and call the relevant functions for the (only)
> subflow in case the mptcp socket is connected to tcp peer.
>
> Reported-by: Christoph Paasch <cpaasch@apple.com>
> Diagnosed-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Florian Westphal <fw@strlen.de>
Applied, thanks Florian.
prev parent reply other threads:[~2020-02-05 13:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 17:12 [PATCH net] mptcp: fix use-after-free on tcp fallback Florian Westphal
2020-02-04 17:44 ` Mat Martineau
2020-02-04 18:05 ` Christoph Paasch
2020-02-05 13:08 ` David Miller [this message]
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