Re: CVE-2024-35840: mptcp: use OPTION_MPTCP_MPJ_SYNACK in subflow_finish_connect()

[Michal Hocko]

Hi,
what is the actual security threat here? As far as I can see, the
problem that the commit requested here addresses seems to be rather
functional, rather than responding to an unexpected packet options with
a reset, we actually establish a connection with some garbage parameters
(likely unpredictable). Which is unfortunate but I do not see any
security implications.

On Fri 17-05-24 16:27:13, Greg KH wrote:
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> mptcp: use OPTION_MPTCP_MPJ_SYNACK in subflow_finish_connect()
> 
> subflow_finish_connect() uses four fields (backup, join_id, thmac, none)
> that may contain garbage unless OPTION_MPTCP_MPJ_SYNACK has been set
> in mptcp_parse_option()
> 
> The Linux kernel CVE team has assigned CVE-2024-35840 to this issue.
> 
> 
> Affected and fixed versions
> ===========================
> 
> 	Issue introduced in 5.7 with commit f296234c98a8 and fixed in 5.15.148 with commit 413b91350732
> 	Issue introduced in 5.7 with commit f296234c98a8 and fixed in 6.1.75 with commit 51e4cb032d49
> 	Issue introduced in 5.7 with commit f296234c98a8 and fixed in 6.6.14 with commit ad3e8f5c3d5c
> 	Issue introduced in 5.7 with commit f296234c98a8 and fixed in 6.7.2 with commit 76e8de7273a2
> 	Issue introduced in 5.7 with commit f296234c98a8 and fixed in 6.8 with commit be1d9d9d38da
> 
> Please see https://www.kernel.org for a full list of currently supported
> kernel versions by the kernel community.
> 
> Unaffected versions might change over time as fixes are backported to
> older supported kernel versions.  The official CVE entry at
> 	https://cve.org/CVERecord/?id=CVE-2024-35840
> will be updated if fixes are backported, please check that for the most
> up to date information about this issue.
> 
> 
> Affected files
> ==============
> 
> The file(s) affected by this issue are:
> 	net/mptcp/subflow.c
> 
> 
> Mitigation
> ==========
> 
> The Linux kernel CVE team recommends that you update to the latest
> stable kernel version for this, and many other bugfixes.  Individual
> changes are never tested alone, but rather are part of a larger kernel
> release.  Cherry-picking individual commits is not recommended or
> supported by the Linux kernel community at all.  If however, updating to
> the latest release is impossible, the individual changes to resolve this
> issue can be found at these commits:
> 	https://git.kernel.org/stable/c/413b913507326972135d2977975dbff8b7f2c453
> 	https://git.kernel.org/stable/c/51e4cb032d49ce094605f27e45eabebc0408893c
> 	https://git.kernel.org/stable/c/ad3e8f5c3d5c53841046ef7a947c04ad45a20721
> 	https://git.kernel.org/stable/c/76e8de7273a22a00d27e9b8b7d4d043d6433416a
> 	https://git.kernel.org/stable/c/be1d9d9d38da922bd4beeec5b6dd821ff5a1dfeb

-- 
Michal Hocko
SUSE Labs