linux-kernel - Re: [PATCH net 1/3] mptcp: Fix data stream corruption in the address announcement

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Message-ID: <20250319153705.GB768132@kernel.org>
Date: Wed, 19 Mar 2025 15:37:05 +0000
From: Simon Horman <horms@...nel.org>
To: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
Cc: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>,
	Geliang Tang <geliang@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Arthur Mongodin <amongodin@...dorisec.fr>, stable@...r.kernel.org
Subject: Re: [PATCH net 1/3] mptcp: Fix data stream corruption in the address
 announcement

On Fri, Mar 14, 2025 at 09:11:31PM +0100, Matthieu Baerts (NGI0) wrote:
> From: Arthur Mongodin <amongodin@...dorisec.fr>
> 
> Because of the size restriction in the TCP options space, the MPTCP
> ADD_ADDR option is exclusive and cannot be sent with other MPTCP ones.
> For this reason, in the linked mptcp_out_options structure, group of
> fields linked to different options are part of the same union.
> 
> There is a case where the mptcp_pm_add_addr_signal() function can modify
> opts->addr, but not ended up sending an ADD_ADDR. Later on, back in
> mptcp_established_options, other options will be sent, but with
> unexpected data written in other fields due to the union, e.g. in
> opts->ext_copy. This could lead to a data stream corruption in the next
> packet.
> 
> Using an intermediate variable, prevents from corrupting previously
> established DSS option. The assignment of the ADD_ADDR option
> parameters is now done once we are sure this ADD_ADDR option can be set
> in the packet, e.g. after having dropped other suboptions.
> 
> Fixes: 1bff1e43a30e ("mptcp: optimize out option generation")
> Cc: stable@...r.kernel.org
> Suggested-by: Paolo Abeni <pabeni@...hat.com>
> Signed-off-by: Arthur Mongodin <amongodin@...dorisec.fr>
> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
> [ Matt: the commit message has been updated: long lines splits and some
>   clarifications. ]
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>

Reviewed-by: Simon Horman <horms@...nel.org>