[PATCH 01/12] drm/client: Fully protect modes[] with dev->mode_config.mutex

[Ville Syrjälä]

On Fri, Apr 05, 2024 at 11:39:33PM +0300, Dmitry Baryshkov wrote:
> On Fri, 5 Apr 2024 at 22:17, Ville Syrjälä
> <ville.syrjala at linux.intel.com> wrote:
> >
> > On Fri, Apr 05, 2024 at 06:24:01AM +0300, Dmitry Baryshkov wrote:
> > > On Thu, Apr 04, 2024 at 11:33:25PM +0300, Ville Syrjala wrote:
> > > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > >
> > > > The modes[] array contains pointers to modes on the connectors'
> > > > mode lists, which are protected by dev->mode_config.mutex.
> > > > Thus we need to extend modes[] the same protection or by the
> > > > time we use it the elements may already be pointing to
> > > > freed/reused memory.
> > > >
> > > > Cc: stable at vger.kernel.org
> > > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10583
> > > > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > >
> > > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> > >
> > > I tried looking for the proper Fixes tag, but it looks like it might be
> > > something like 386516744ba4 ("drm/fb: fix fbdev object model + cleanup properly.")
> >
> > The history is rather messy. I think it was originally completely
> > lockless and broken, and got fixed piecemeal later in these:
> > commit 7394371d8569 ("drm: Take lock around probes for drm_fb_helper_hotplug_event")
> > commit 966a6a13c666 ("drm: Hold mode_config.lock to prevent hotplug whilst setting up crtcs")
> >
> > commit e13a05831050 ("drm/fb-helper: Stop using mode_config.mutex for internals")
> > looks to me like where the race might have been re-introduced.
> > But didn't do a thorough analysis so not 100% sure. It's all
> > rather ancient history by now so a Fixes tag doesn't seem all
> > that useful anyway.
> 
> Well, you have added stable to cc list, so you expect to have this
> patch backported. Then it should either have a kernel version as a
> 'starting' point or a Fixes tag to assist the sable team.

It'll get backported just fine without either.

-- 
Ville Syrjälä
Intel