netdev - Re: [PATCH net] tcp: add a missing nf_reset

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Message-ID: <403746c5-8c4a-02e6-cbb8-b43116ad9f18@ovn.org>
Date:   Thu, 23 Jun 2022 13:48:46 +0200
From:   Ilya Maximets <i.maximets@....org>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     i.maximets@....org, netdev@...r.kernel.org, eric.dumazet@...il.com,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: [PATCH net] tcp: add a missing nf_reset_ct() in 3WHS handling

On 6/23/22 07:04, Eric Dumazet wrote:
> When the third packet of 3WHS connection establishment
> contains payload, it is added into socket receive queue
> without the XFRM check and the drop of connection tracking
> context.
> 
> This means that if the data is left unread in the socket
> receive queue, conntrack module can not be unloaded.
> 
> As most applications usually reads the incoming data
> immediately after accept(), bug has been hiding for
> quite a long time.
> 
> Commit 68822bdf76f1 ("net: generalize skb freeing
> deferral to per-cpu lists") exposed this bug because
> even if the application reads this data, the skb
> with nfct state could stay in a per-cpu cache for
> an arbitrary time, if said cpu no longer process RX softirqs.
> 
> Many thanks to Ilya Maximets for reporting this issue,
> and for testing various patches:
> https://lore.kernel.org/netdev/20220619003919.394622-1-i.maximets@ovn.org/
> 
> Note that I also added a missing xfrm4_policy_check() call,
> although this is probably not a big issue, as the SYN
> packet should have been dropped earlier.
> 
> Fixes: b59c270104f0 ("[NETFILTER]: Keep conntrack reference until IPsec policy checks are done")
> Reported-by: Ilya Maximets <i.maximets@....org>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Florian Westphal <fw@...len.de>
> Cc: Pablo Neira Ayuso <pablo@...filter.org>
> Cc: Steffen Klassert <steffen.klassert@...unet.com>
> ---
>  net/ipv4/tcp_ipv4.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

Thanks!  I re-tested this change with the OVS testsuite
and it works fine.  It can successfully reload ntfilter
modules now.  So, for the nf_reset_ct part of the fix:

Tested-by: Ilya Maximets <i.maximets@....org>
Reviewed-by: Ilya Maximets <i.maximets@....org>

XFRM part seems correct to me, but I didn't test it.