ACK/Cmnt: [SRU][J][PATCH 0/1] CVE-2022-50071

[Edoardo Canepa]

Acked-by: Edoardo Canepa <edoardo.canepa at canonical.com>

drop the trailing mptcp_dispose_initial_subflow()
above sock_put() in __mptcp_destroy_sock(). Upstream's only call was
before the close loop and c0bf3c6aa444 moves it; 5.15's second copy at
the end is untouched by the diff and is now a guaranteed no-op.

On 9/10/26 08:35, Cengiz Can via kernel-team wrote:
> https://ubuntu.com/security/CVE-2022-50071
>
> [ Impact ]
>
> In the Linux kernel, the following vulnerability has been resolved:
>
> mptcp: move subflow cleanup in mptcp_destroy_common()
>
> If the mptcp socket creation fails due to a CGROUP_INET_SOCK_CREATE eBPF
> program, the MPTCP protocol ends-up leaking all the subflows: the related
> cleanup happens in __mptcp_destroy_sock() that is not invoked in such code
> path.
>
> Address the issue moving the subflow sockets cleanup in the
> mptcp_destroy_common() helper, which is invoked in every msk cleanup path.
>
> Additionally get rid of the intermediate list_splice_init step, which is an
> unneeded relic from the past.
>
> The issue is present since before the reported root cause commit, but any
> attempt to backport the fix before that hash will require a complete rewrite.
>
> [ Fix ]
>
> jammy/linux: backported from c0bf3c6aa444
>
> [ Test Plan ]
>
> Build and boot tested.
>
> [ Where Problems Could Occur ]
>
> This change reorganizes the socket teardown path for Multipath TCP (MPTCP),
> so any regression would surface on hosts that enable and use MPTCP,
> particularly network-facing workloads that open and close MPTCP connections
> frequently; a bad fix could double-free or otherwise mishandle subflow
> sockets during msk cleanup. Systems that do not use MPTCP are not affected.
>
> [ Other Info ]
>
> Kybele flow-v11-25-ga27c0fa6. Reference: fba91963/v1
>
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