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

[Cengiz Can]

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