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Message-ID: <2024100142-trespass-likewise-015a@gregkh> Date: Tue, 1 Oct 2024 15:53:59 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Michal Hocko <mhocko@...e.com> Cc: Petr Mladek <pmladek@...e.com>, cve@...nel.org, linux-kernel@...r.kernel.org, linux-cve-announce@...r.kernel.org, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Nicholas Piggin <npiggin@...il.com>, "Paul E. McKenney" <paulmck@...nel.org>, Tejun Heo <tj@...nel.org>, Sasha Levin <sashal@...nel.org>, Michal Koutný <mkoutny@...e.com> Subject: Re: CVE-2024-46839: workqueue: Improve scalability of workqueue watchdog touch On Tue, Oct 01, 2024 at 11:07:49AM +0200, Michal Hocko wrote: > On Tue 01-10-24 10:22:51, Greg KH wrote: > > On Tue, Oct 01, 2024 at 10:02:02AM +0200, Petr Mladek wrote: > > > On Fri 2024-09-27 14:40:07, Greg Kroah-Hartman wrote: > > > > Description > > > > =========== > > > > > > > > In the Linux kernel, the following vulnerability has been resolved: > > > > > > > > workqueue: Improve scalability of workqueue watchdog touch > > > > > > > > On a ~2000 CPU powerpc system, hard lockups have been observed in the > > > > workqueue code when stop_machine runs (in this case due to CPU hotplug). > > > > > > I believe that this does not qualify as a security vulnerability. > > > Any hotplug is a privileged operation. > > > > Really? I see that happen on many embedded systems all the time, they > > add/remove CPUs while the device runs/sleeps constantly. > > This is a powerpc specific fix. Other architectures are not affected. > > > Now to be fair, right now an "embedded system" usually doesn't have 2000 > > cpus, but what's wrong with marking this real bugfix as a vulnerability > > resolution? > > Yes, this is indeed a scalability fix for huge systems with a lot of > CPUs anybody owning those systems was simply not able to use memory > hotplug without seeing those hard lockup messages. The system is not > really locked up. The progress of the hotplug operation is just utterly > slow. Calling this a vulnerability is a stretch IMHO. > > The only potential attack vector is to have machine configured to panic > on hard lockups on those huge ppc systems and allow cpu hotremove to an > adversary which in itsels seems like a very bad idea anyway because > availability of such a system is then effectively compromised. Ok, now rejected, thanks. greg k-h
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