netdev - Re: [PATCH net] socket, bpf: fix possible use after free

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Message-ID: <59D296AE.3080102@iogearbox.net>
Date:   Mon, 02 Oct 2017 21:42:38 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>
CC:     netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH net] socket, bpf: fix possible use after free

On 10/02/2017 09:20 PM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Starting from linux-4.4, 3WHS no longer takes the listener lock.
>
> Since this time, we might hit a use-after-free in sk_filter_charge(),
> if the filter we got in the memcpy() of the listener content
> just happened to be replaced by a thread changing listener BPF filter.
>
> To fix this, we need to make sure the filter refcount is not already
> zero before incrementing it again.
>
> Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Thanks, Eric!

Acked-by: Daniel Borkmann <daniel@...earbox.net>