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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Jun 17, 2024 at 05:59:30PM +0200, Michal Hocko wrote:
> On Mon 17-06-24 17:43:10, Greg KH wrote:
> > On Thu, Jun 06, 2024 at 10:03:54AM +0200, Michal Hocko wrote:
> > > 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.
> > 
> > Sorry for the delay.  I'm pretty sure this is a data leak as the
> > "garbage" is coming from other kernel data, and as such, was reviewed by
> > us as a vulnerability.
> 
> This is not my area so bear with me, but isn't the garbage coming from a
> remote side of the connection so it is just a garbage? I would
> understand that a misbehavior on the receiving end could be considered
> problematic but I still do not see this happening. Or am I wrong?

I do not know, I thought it was coming from the local kernel memory.
I'll defer here to the network developers to answer it for sure.

thanks,

greg k-h