[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Zmq8uSVv0X5f7xx+@duo.ucw.cz>
Date: Thu, 13 Jun 2024 11:32:41 +0200
From: Pavel Machek <pavel@....cz>
To: Lee Jones <lee@...nel.org>
Cc: Michal Hocko <mhocko@...e.com>, cve@...nel.org,
linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Felix Kuehling <felix.kuehling@....com>
Subject: Re: CVE-2024-26628: drm/amdkfd: Fix lock dependency warning
On Wed 2024-03-20 15:47:34, Lee Jones wrote:
> On Wed, 20 Mar 2024, Michal Hocko wrote:
>
> > On Thu 14-03-24 11:09:38, Lee Jones wrote:
> > > On Fri, 08 Mar 2024, Michal Hocko wrote:
> > >
> > > > On Wed 06-03-24 06:46:11, Greg KH wrote:
> > > > [...]
> > > > > Possible unsafe locking scenario:
> > > > >
> > > > > CPU0 CPU1
> > > > > ---- ----
> > > > > lock(&svms->lock);
> > > > > lock(&mm->mmap_lock);
> > > > > lock(&svms->lock);
> > > > > lock((work_completion)(&svm_bo->eviction_work));
> > > > >
> > > > > I believe this cannot really lead to a deadlock in practice, because
> > > > > svm_range_evict_svm_bo_worker only takes the mmap_read_lock if the BO
> > > > > refcount is non-0. That means it's impossible that svm_range_bo_release
> > > > > is running concurrently. However, there is no good way to annotate this.
> > > >
> > > > OK, so is this even a bug (not to mention a security/weakness)?
> > >
> > > Looks like the patch fixes a warning which can crash some kernels. So
> > > the CVE appears to be fixing that, rather than the impossible deadlock.
> >
> > Are you talking about lockdep warning or anything else?
>
> Anything that triggers a BUG() or a WARN() (as per the splat in the
> commit message). Many in-field kernels are configured to panic on
> BUG()s and WARN()s, thus triggering them are presently considered local
> DoS and attract CVE status.
So... because it is possible to configure machine to reboot on
warning, now every warning is a security issue?
Lockdep is for debugging, if someone uses it in production with panic
on reboot, they are getting exactly what they are asking for.
Not a security problem.
Pavel
--
People of Russia, stop Putin before his war on Ukraine escalates.
Download attachment "signature.asc" of type "application/pgp-signature" (196 bytes)
Powered by blists - more mailing lists