Re: [PATCH 01/12] drm/client: Fully protect modes[] with dev->mode_config.mutex
On Fri, Apr 05, 2024 at 11:39:33PM +0300, Dmitry Baryshkov wrote:
> On Fri, 5 Apr 2024 at 22:17, Ville Syrjälä
> 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
> > > >
> > > > 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: sta...@vger.kernel.org
> > > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10583
> > > > Signed-off-by: Ville Syrjälä
> > >
> > > Reviewed-by: Dmitry Baryshkov
> > >
> > > 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
Re: [PATCH 01/12] drm/client: Fully protect modes[] with dev->mode_config.mutex
On Fri, 5 Apr 2024 at 22:17, Ville Syrjälä
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
> > >
> > > 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: sta...@vger.kernel.org
> > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10583
> > > Signed-off-by: Ville Syrjälä
> >
> > Reviewed-by: Dmitry Baryshkov
> >
> > 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.
--
With best wishes
Dmitry
Re: [PATCH 01/12] drm/client: Fully protect modes[] with dev->mode_config.mutex
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
> >
> > 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: sta...@vger.kernel.org
> > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10583
> > Signed-off-by: Ville Syrjälä
>
> Reviewed-by: Dmitry Baryshkov
>
> 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.
--
Ville Syrjälä
Intel
Re: [PATCH 01/12] drm/client: Fully protect modes[] with dev->mode_config.mutex
On Thu, Apr 04, 2024 at 11:33:25PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä
>
> 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: sta...@vger.kernel.org
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10583
> Signed-off-by: Ville Syrjälä
Reviewed-by: Dmitry Baryshkov
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.")
> ---
> drivers/gpu/drm/drm_client_modeset.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_client_modeset.c
> b/drivers/gpu/drm/drm_client_modeset.c
> index 871e4e2129d6..0683a129b362 100644
> --- a/drivers/gpu/drm/drm_client_modeset.c
> +++ b/drivers/gpu/drm/drm_client_modeset.c
> @@ -777,6 +777,7 @@ int drm_client_modeset_probe(struct drm_client_dev
> *client, unsigned int width,
> unsigned int total_modes_count = 0;
> struct drm_client_offset *offsets;
> unsigned int connector_count = 0;
> + /* points to modes protected by mode_config.mutex */
> struct drm_display_mode **modes;
> struct drm_crtc **crtcs;
> int i, ret = 0;
> @@ -845,7 +846,6 @@ int drm_client_modeset_probe(struct drm_client_dev
> *client, unsigned int width,
> drm_client_pick_crtcs(client, connectors, connector_count,
> crtcs, modes, 0, width, height);
> }
> - mutex_unlock(>mode_config.mutex);
>
> drm_client_modeset_release(client);
>
> @@ -875,6 +875,7 @@ int drm_client_modeset_probe(struct drm_client_dev
> *client, unsigned int width,
> modeset->y = offset->y;
> }
> }
> + mutex_unlock(>mode_config.mutex);
>
> mutex_unlock(>modeset_mutex);
> out:
> --
> 2.43.2
>
--
With best wishes
Dmitry
[PATCH 01/12] drm/client: Fully protect modes[] with dev->mode_config.mutex
From: Ville Syrjälä 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: sta...@vger.kernel.org Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10583 Signed-off-by: Ville Syrjälä --- drivers/gpu/drm/drm_client_modeset.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c index 871e4e2129d6..0683a129b362 100644 --- a/drivers/gpu/drm/drm_client_modeset.c +++ b/drivers/gpu/drm/drm_client_modeset.c @@ -777,6 +777,7 @@ int drm_client_modeset_probe(struct drm_client_dev *client, unsigned int width, unsigned int total_modes_count = 0; struct drm_client_offset *offsets; unsigned int connector_count = 0; + /* points to modes protected by mode_config.mutex */ struct drm_display_mode **modes; struct drm_crtc **crtcs; int i, ret = 0; @@ -845,7 +846,6 @@ int drm_client_modeset_probe(struct drm_client_dev *client, unsigned int width, drm_client_pick_crtcs(client, connectors, connector_count, crtcs, modes, 0, width, height); } - mutex_unlock(>mode_config.mutex); drm_client_modeset_release(client); @@ -875,6 +875,7 @@ int drm_client_modeset_probe(struct drm_client_dev *client, unsigned int width, modeset->y = offset->y; } } + mutex_unlock(>mode_config.mutex); mutex_unlock(>modeset_mutex); out: -- 2.43.2
