[PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Brian Norris]

It's possible for users to try to duplicate the CRTC state even when the
state doesn't exist. drm_atomic_helper_crtc_duplicate_state() (and other
users of __drm_atomic_helper_crtc_duplicate_state()) already guard this
with a WARN_ON() instead of crashing, so let's do that here too.

Signed-off-by: Brian Norris <briannorris@chromium.org>
---

 drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index 74562d40f639..daf192881353 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
@@ -1570,6 +1570,9 @@ static struct drm_crtc_state *vop_crtc_duplicate_state(struct drm_crtc *crtc)
 {
 	struct rockchip_crtc_state *rockchip_state;
 
+	if (WARN_ON(!crtc->state))
+		return NULL;
+
 	rockchip_state = kzalloc(sizeof(*rockchip_state), GFP_KERNEL);
 	if (!rockchip_state)
 		return NULL;
-- 
2.36.1.476.g0c4daa206d-goog

Re: [PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Sean Paul]

On Fri, Jun 17, 2022 at 05:26:52PM -0700, Brian Norris wrote:
> It's possible for users to try to duplicate the CRTC state even when the
> state doesn't exist. drm_atomic_helper_crtc_duplicate_state() (and other
> users of __drm_atomic_helper_crtc_duplicate_state()) already guard this
> with a WARN_ON() instead of crashing, so let's do that here too.
> 
> Signed-off-by: Brian Norris <briannorris@chromium.org>

Thanks for this patch!

Reviewed-by: Sean Paul <seanpaul@chromium.org>

> ---
> 
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 74562d40f639..daf192881353 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -1570,6 +1570,9 @@ static struct drm_crtc_state *vop_crtc_duplicate_state(struct drm_crtc *crtc)
>  {
>  	struct rockchip_crtc_state *rockchip_state;
>  
> +	if (WARN_ON(!crtc->state))
> +		return NULL;
> +
>  	rockchip_state = kzalloc(sizeof(*rockchip_state), GFP_KERNEL);
>  	if (!rockchip_state)
>  		return NULL;
> -- 
> 2.36.1.476.g0c4daa206d-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS

Re: [PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Doug Anderson]

Hi,

On Fri, Jun 17, 2022 at 5:27 PM Brian Norris <briannorris@chromium.org> wrote:
>
> It's possible for users to try to duplicate the CRTC state even when the
> state doesn't exist. drm_atomic_helper_crtc_duplicate_state() (and other
> users of __drm_atomic_helper_crtc_duplicate_state()) already guard this
> with a WARN_ON() instead of crashing, so let's do that here too.
>
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
>
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 3 +++
>  1 file changed, 3 insertions(+)

I'm not an expert in this area, but it makes sense to me to match
drm_atomic_helper_crtc_duplicate_state() in this way. Thus:

Reviewed-by: Douglas Anderson <dianders@chromium.org>

I would tend to assume that this would be landed in drm-misc by Heiko
if he's good with it. After several weeks of silence, however, I'll
commit it myself.

-Doug

Re: [PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Heiko Stuebner]

Am Freitag, 24. Juni 2022, 01:44:52 CEST schrieb Doug Anderson:
> Hi,
> 
> On Fri, Jun 17, 2022 at 5:27 PM Brian Norris <briannorris@chromium.org> wrote:
> >
> > It's possible for users to try to duplicate the CRTC state even when the
> > state doesn't exist. drm_atomic_helper_crtc_duplicate_state() (and other
> > users of __drm_atomic_helper_crtc_duplicate_state()) already guard this
> > with a WARN_ON() instead of crashing, so let's do that here too.
> >
> > Signed-off-by: Brian Norris <briannorris@chromium.org>
> > ---
> >
> >  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 3 +++
> >  1 file changed, 3 insertions(+)
> 
> I'm not an expert in this area, but it makes sense to me to match
> drm_atomic_helper_crtc_duplicate_state() in this way. Thus:
> 
> Reviewed-by: Douglas Anderson <dianders@chromium.org>
> 
> I would tend to assume that this would be landed in drm-misc by Heiko
> if he's good with it. After several weeks of silence, however, I'll
> commit it myself.

I do tend to batch up drm-misc patches, as that is always a different
workflow but I'll pick that up :-)

The interesting question would be, do we want some fixes tag for it?


Heiko

Re: [PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Brian Norris]

On Fri, Jun 24, 2022 at 12:23 AM Heiko Stuebner <heiko@sntech.de> wrote:
> The interesting question would be, do we want some fixes tag for it?

I'm not aware of any currently-upstream code that will hit this [1].
I've hit it in out-of-tree code (or, code that I submitted to
dri-devel, but wasn't accepted as-is), and this is the "belt and
braces" part -- the primary fix is that we should avoid calling things
like drm_atomic_get_crtc_state() at inappropriate times.

So, is the "extra safety" check really something that should go to
-stable? (Because let's be honest, everything with a Fixes tag goes
there.) Maybe?

Anyway, if you want to "blame" anything, this commit actually dropped
the safety check:

4e257d9eee23 drm/rockchip: get rid of rockchip_drm_crtc_mode_config

Brian

[1] But I'm not omniscient. So maybe it's good to have anyway.

Re: [PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Heiko Stuebner]

Am Freitag, 24. Juni 2022, 19:57:53 CEST schrieb Brian Norris:
> On Fri, Jun 24, 2022 at 12:23 AM Heiko Stuebner <heiko@sntech.de> wrote:
> > The interesting question would be, do we want some fixes tag for it?
> 
> I'm not aware of any currently-upstream code that will hit this [1].
> I've hit it in out-of-tree code (or, code that I submitted to
> dri-devel, but wasn't accepted as-is), and this is the "belt and
> braces" part -- the primary fix is that we should avoid calling things
> like drm_atomic_get_crtc_state() at inappropriate times.
> 
> So, is the "extra safety" check really something that should go to
> -stable? (Because let's be honest, everything with a Fixes tag goes
> there.) Maybe?
> 
> Anyway, if you want to "blame" anything, this commit actually dropped
> the safety check:
> 
> 4e257d9eee23 drm/rockchip: get rid of rockchip_drm_crtc_mode_config

I tend to think, if we know that connection we should also include it :-) .
I wouldn't include a cc-stable for the reason you mentioned, but to me
it makes sense if someone reading the git history in the future can easily
know that information - so it doesn't hurt :-) .

So I'll add that when applying.

Thanks for supplying the origin commit
Heiko

> 
> Brian
> 
> [1] But I'm not omniscient. So maybe it's good to have anyway.
> 

Re: [PATCH] drm/rockchip: vop: Don't crash for invalid duplicate_state()

[Heiko Stuebner]

On Fri, 17 Jun 2022 17:26:52 -0700, Brian Norris wrote:
> It's possible for users to try to duplicate the CRTC state even when the
> state doesn't exist. drm_atomic_helper_crtc_duplicate_state() (and other
> users of __drm_atomic_helper_crtc_duplicate_state()) already guard this
> with a WARN_ON() instead of crashing, so let's do that here too.

Applied, thanks!

[1/1] drm/rockchip: vop: Don't crash for invalid duplicate_state()
      commit: 1449110b0dade8b638d2c17ab7c5b0ff696bfccb

Best regards,
-- 
Heiko Stuebner <heiko@sntech.de>