[PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

It is possible that drm_simple_kms_plane_atomic_check called
with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
to 0 before doing any actual drawing. This leads to NULL pointer
dereference because in this case new CRTC state is NULL and must be
checked before accessing.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 9ca8a4a59b74..a05eca9cec8b 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
 	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
 						   &pipe->crtc);
-	if (!crtc_state->enable)
-		return 0; /* nothing to check when disabling or disabled */
+
+	if (!crtc_state || !crtc_state->enable)
+		/* nothing to check when disabling or disabled or no CRTC set */
+		return 0;
 
 	if (crtc_state->enable)
 		drm_mode_get_hv_timing(&crtc_state->mode,
-- 
2.7.4

[PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

It is possible that drm_simple_kms_plane_atomic_check called
with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
to 0 before doing any actual drawing. This leads to NULL pointer
dereference because in this case new CRTC state is NULL and must be
checked before accessing.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 9ca8a4a59b74..a05eca9cec8b 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
 	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
 						   &pipe->crtc);
-	if (!crtc_state->enable)
-		return 0; /* nothing to check when disabling or disabled */
+
+	if (!crtc_state || !crtc_state->enable)
+		/* nothing to check when disabling or disabled or no CRTC set */
+		return 0;
 
 	if (crtc_state->enable)
 		drm_mode_get_hv_timing(&crtc_state->mode,
-- 
2.7.4

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Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> 
> It is possible that drm_simple_kms_plane_atomic_check called
> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> to 0 before doing any actual drawing. This leads to NULL pointer
> dereference because in this case new CRTC state is NULL and must be
> checked before accessing.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 9ca8a4a59b74..a05eca9cec8b 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>  	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>  	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>  						   &pipe->crtc);
> -	if (!crtc_state->enable)
> -		return 0; /* nothing to check when disabling or disabled */
> +
> +	if (!crtc_state || !crtc_state->enable)
> +		/* nothing to check when disabling or disabled or no CRTC set */
> +		return 0;
>  
>  	if (crtc_state->enable)
>  		drm_mode_get_hv_timing(&crtc_state->mode,

Hm, this is a bit annoying, since the can_position = false parameter to
drm_atomic_helper_check_plane_state is supposed to catch all this. Would
moving all the checks after the call to that helper, and gating them on
plane_state->visible also work?

We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
it can cope with crtc_state == NULL, but I think that's a good idea
anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
case.

Otherwise we'll just go with your fix, but it feels all a bit too fragile,
hence why I want to explore more robust options a bit.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> 
> It is possible that drm_simple_kms_plane_atomic_check called
> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> to 0 before doing any actual drawing. This leads to NULL pointer
> dereference because in this case new CRTC state is NULL and must be
> checked before accessing.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 9ca8a4a59b74..a05eca9cec8b 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>  	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>  	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>  						   &pipe->crtc);
> -	if (!crtc_state->enable)
> -		return 0; /* nothing to check when disabling or disabled */
> +
> +	if (!crtc_state || !crtc_state->enable)
> +		/* nothing to check when disabling or disabled or no CRTC set */
> +		return 0;
>  
>  	if (crtc_state->enable)
>  		drm_mode_get_hv_timing(&crtc_state->mode,

Hm, this is a bit annoying, since the can_position = false parameter to
drm_atomic_helper_check_plane_state is supposed to catch all this. Would
moving all the checks after the call to that helper, and gating them on
plane_state->visible also work?

We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
it can cope with crtc_state == NULL, but I think that's a good idea
anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
case.

Otherwise we'll just go with your fix, but it feels all a bit too fragile,
hence why I want to explore more robust options a bit.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> It is possible that drm_simple_kms_plane_atomic_check called
>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>> to 0 before doing any actual drawing. This leads to NULL pointer
>> dereference because in this case new CRTC state is NULL and must be
>> checked before accessing.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>> index 9ca8a4a59b74..a05eca9cec8b 100644
>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>   	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>   	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>   						   &pipe->crtc);
>> -	if (!crtc_state->enable)
>> -		return 0; /* nothing to check when disabling or disabled */
>> +
>> +	if (!crtc_state || !crtc_state->enable)
>> +		/* nothing to check when disabling or disabled or no CRTC set */
>> +		return 0;
>>   
>>   	if (crtc_state->enable)
>>   		drm_mode_get_hv_timing(&crtc_state->mode,
> Hm, this is a bit annoying, since the can_position = false parameter to
> drm_atomic_helper_check_plane_state is supposed to catch all this. Would
> moving all the checks after the call to that helper, and gating them on
> plane_state->visible also work?
Yes, it does work if this is what you mean:
diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c 
b/drivers/gpu/drm/drm_simple_kms_helper.c
index a05eca9cec8b..c48858bb2823 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct 
drm_plane *plane,
         crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
&pipe->crtc);

-       if (!crtc_state || !crtc_state->enable)
-               /* nothing to check when disabling or disabled or no 
CRTC set */
-               return 0;
-
-       if (crtc_state->enable)
-               drm_mode_get_hv_timing(&crtc_state->mode,
-                                      &clip.x2, &clip.y2);
-
         ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
                                                   &clip,
DRM_PLANE_HELPER_NO_SCALING,
@@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct 
drm_plane *plane,
         if (ret)
                 return ret;

+       if (!plane_state->visible || !crtc_state->enable)
+               return 0; /* nothing to check when disabling or disabled */
+
+       if (plane_state->visible && crtc_state->enable)
+               drm_mode_get_hv_timing(&crtc_state->mode,
+                                      &clip.x2, &clip.y2);
+
         if (!plane_state->visible)
                 return -EINVAL;

> We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
> it can cope with crtc_state == NULL, but I think that's a good idea
> anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
> case.
It doesn't look at it at the moment
> Otherwise we'll just go with your fix, but it feels all a bit too fragile,
> hence why I want to explore more robust options a bit.
At list with the change above it passes my test which failed
before. Although I cannot confirm it works for others, but it
certainly does for me.
> -Daniel
Do you want me to send v1 with the code above?

Thank you,
Oleksandr

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> It is possible that drm_simple_kms_plane_atomic_check called
>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>> to 0 before doing any actual drawing. This leads to NULL pointer
>> dereference because in this case new CRTC state is NULL and must be
>> checked before accessing.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>> index 9ca8a4a59b74..a05eca9cec8b 100644
>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>   	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>   	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>   						   &pipe->crtc);
>> -	if (!crtc_state->enable)
>> -		return 0; /* nothing to check when disabling or disabled */
>> +
>> +	if (!crtc_state || !crtc_state->enable)
>> +		/* nothing to check when disabling or disabled or no CRTC set */
>> +		return 0;
>>   
>>   	if (crtc_state->enable)
>>   		drm_mode_get_hv_timing(&crtc_state->mode,
> Hm, this is a bit annoying, since the can_position = false parameter to
> drm_atomic_helper_check_plane_state is supposed to catch all this. Would
> moving all the checks after the call to that helper, and gating them on
> plane_state->visible also work?
Yes, it does work if this is what you mean:
diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c 
b/drivers/gpu/drm/drm_simple_kms_helper.c
index a05eca9cec8b..c48858bb2823 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct 
drm_plane *plane,
         crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
&pipe->crtc);

-       if (!crtc_state || !crtc_state->enable)
-               /* nothing to check when disabling or disabled or no 
CRTC set */
-               return 0;
-
-       if (crtc_state->enable)
-               drm_mode_get_hv_timing(&crtc_state->mode,
-                                      &clip.x2, &clip.y2);
-
         ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
                                                   &clip,
DRM_PLANE_HELPER_NO_SCALING,
@@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct 
drm_plane *plane,
         if (ret)
                 return ret;

+       if (!plane_state->visible || !crtc_state->enable)
+               return 0; /* nothing to check when disabling or disabled */
+
+       if (plane_state->visible && crtc_state->enable)
+               drm_mode_get_hv_timing(&crtc_state->mode,
+                                      &clip.x2, &clip.y2);
+
         if (!plane_state->visible)
                 return -EINVAL;

> We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
> it can cope with crtc_state == NULL, but I think that's a good idea
> anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
> case.
It doesn't look at it at the moment
> Otherwise we'll just go with your fix, but it feels all a bit too fragile,
> hence why I want to explore more robust options a bit.
At list with the change above it passes my test which failed
before. Although I cannot confirm it works for others, but it
certainly does for me.
> -Daniel
Do you want me to send v1 with the code above?

Thank you,
Oleksandr
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Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> > On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
> > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > 
> > > It is possible that drm_simple_kms_plane_atomic_check called
> > > with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> > > to 0 before doing any actual drawing. This leads to NULL pointer
> > > dereference because in this case new CRTC state is NULL and must be
> > > checked before accessing.
> > > 
> > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > ---
> > >   drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
> > >   1 file changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > index 9ca8a4a59b74..a05eca9cec8b 100644
> > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> > >   	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> > >   	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > >   						   &pipe->crtc);
> > > -	if (!crtc_state->enable)
> > > -		return 0; /* nothing to check when disabling or disabled */
> > > +
> > > +	if (!crtc_state || !crtc_state->enable)
> > > +		/* nothing to check when disabling or disabled or no CRTC set */
> > > +		return 0;
> > >   	if (crtc_state->enable)
> > >   		drm_mode_get_hv_timing(&crtc_state->mode,
> > Hm, this is a bit annoying, since the can_position = false parameter to
> > drm_atomic_helper_check_plane_state is supposed to catch all this. Would
> > moving all the checks after the call to that helper, and gating them on
> > plane_state->visible also work?
> Yes, it does work if this is what you mean:

I wasn't sure, thanks for figuring this out!

> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
> b/drivers/gpu/drm/drm_simple_kms_helper.c
> index a05eca9cec8b..c48858bb2823 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
> drm_plane *plane,
>         crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> &pipe->crtc);
> 
> -       if (!crtc_state || !crtc_state->enable)
> -               /* nothing to check when disabling or disabled or no CRTC
> set */
> -               return 0;
> -
> -       if (crtc_state->enable)
> -               drm_mode_get_hv_timing(&crtc_state->mode,
> -                                      &clip.x2, &clip.y2);
> -
>         ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>                                                   &clip,
> DRM_PLANE_HELPER_NO_SCALING,
> @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
> drm_plane *plane,
>         if (ret)
>                 return ret;
> 
> +       if (!plane_state->visible || !crtc_state->enable)
> +               return 0; /* nothing to check when disabling or disabled */

if (!plane_state->visible) {
	WARN_ON(crtc_state->enabled);
	return 0;
}

The helper call above should guarantee this.
> +
> +       if (plane_state->visible && crtc_state->enable)

Similar here.

> +               drm_mode_get_hv_timing(&crtc_state->mode,
> +                                      &clip.x2, &clip.y2);
> +
>         if (!plane_state->visible)
>                 return -EINVAL;

This can now be removed, the plane helper takes care of checking for
plane_state->visible != crtc_state->enable. Please also remove.

> > We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
> > it can cope with crtc_state == NULL, but I think that's a good idea
> > anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
> > case.
> It doesn't look at it at the moment
> > Otherwise we'll just go with your fix, but it feels all a bit too fragile,
> > hence why I want to explore more robust options a bit.
> At list with the change above it passes my test which failed
> before. Although I cannot confirm it works for others, but it
> certainly does for me.
> > -Daniel
> Do you want me to send v1 with the code above?

Yes please, with my above cleanup suggestions.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> > On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
> > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > 
> > > It is possible that drm_simple_kms_plane_atomic_check called
> > > with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> > > to 0 before doing any actual drawing. This leads to NULL pointer
> > > dereference because in this case new CRTC state is NULL and must be
> > > checked before accessing.
> > > 
> > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > ---
> > >   drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
> > >   1 file changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > index 9ca8a4a59b74..a05eca9cec8b 100644
> > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> > >   	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> > >   	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > >   						   &pipe->crtc);
> > > -	if (!crtc_state->enable)
> > > -		return 0; /* nothing to check when disabling or disabled */
> > > +
> > > +	if (!crtc_state || !crtc_state->enable)
> > > +		/* nothing to check when disabling or disabled or no CRTC set */
> > > +		return 0;
> > >   	if (crtc_state->enable)
> > >   		drm_mode_get_hv_timing(&crtc_state->mode,
> > Hm, this is a bit annoying, since the can_position = false parameter to
> > drm_atomic_helper_check_plane_state is supposed to catch all this. Would
> > moving all the checks after the call to that helper, and gating them on
> > plane_state->visible also work?
> Yes, it does work if this is what you mean:

I wasn't sure, thanks for figuring this out!

> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
> b/drivers/gpu/drm/drm_simple_kms_helper.c
> index a05eca9cec8b..c48858bb2823 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
> drm_plane *plane,
>         crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> &pipe->crtc);
> 
> -       if (!crtc_state || !crtc_state->enable)
> -               /* nothing to check when disabling or disabled or no CRTC
> set */
> -               return 0;
> -
> -       if (crtc_state->enable)
> -               drm_mode_get_hv_timing(&crtc_state->mode,
> -                                      &clip.x2, &clip.y2);
> -
>         ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>                                                   &clip,
> DRM_PLANE_HELPER_NO_SCALING,
> @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
> drm_plane *plane,
>         if (ret)
>                 return ret;
> 
> +       if (!plane_state->visible || !crtc_state->enable)
> +               return 0; /* nothing to check when disabling or disabled */

if (!plane_state->visible) {
	WARN_ON(crtc_state->enabled);
	return 0;
}

The helper call above should guarantee this.
> +
> +       if (plane_state->visible && crtc_state->enable)

Similar here.

> +               drm_mode_get_hv_timing(&crtc_state->mode,
> +                                      &clip.x2, &clip.y2);
> +
>         if (!plane_state->visible)
>                 return -EINVAL;

This can now be removed, the plane helper takes care of checking for
plane_state->visible != crtc_state->enable. Please also remove.

> > We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
> > it can cope with crtc_state == NULL, but I think that's a good idea
> > anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
> > case.
> It doesn't look at it at the moment
> > Otherwise we'll just go with your fix, but it feels all a bit too fragile,
> > hence why I want to explore more robust options a bit.
> At list with the change above it passes my test which failed
> before. Although I cannot confirm it works for others, but it
> certainly does for me.
> > -Daniel
> Do you want me to send v1 with the code above?

Yes please, with my above cleanup suggestions.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

[-- Attachment #1: Type: text/plain, Size: 8470 bytes --]

On 02/20/2018 01:17 PM, Daniel Vetter wrote:
> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>
>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>> dereference because in this case new CRTC state is NULL and must be
>>>> checked before accessing.
>>>>
>>>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>> ---
>>>>    drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>    	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>>>    	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>>    						   &pipe->crtc);
>>>> -	if (!crtc_state->enable)
>>>> -		return 0; /* nothing to check when disabling or disabled */
>>>> +
>>>> +	if (!crtc_state || !crtc_state->enable)
>>>> +		/* nothing to check when disabling or disabled or no CRTC set */
>>>> +		return 0;
>>>>    	if (crtc_state->enable)
>>>>    		drm_mode_get_hv_timing(&crtc_state->mode,
>>> Hm, this is a bit annoying, since the can_position = false parameter to
>>> drm_atomic_helper_check_plane_state is supposed to catch all this. Would
>>> moving all the checks after the call to that helper, and gating them on
>>> plane_state->visible also work?
>> Yes, it does work if this is what you mean:
> I wasn't sure, thanks for figuring this out!
>
>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>> index a05eca9cec8b..c48858bb2823 100644
>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>> @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
>> drm_plane *plane,
>>          crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>> &pipe->crtc);
>>
>> -       if (!crtc_state || !crtc_state->enable)
>> -               /* nothing to check when disabling or disabled or no CRTC
>> set */
>> -               return 0;
>> -
>> -       if (crtc_state->enable)
>> -               drm_mode_get_hv_timing(&crtc_state->mode,
>> -                                      &clip.x2, &clip.y2);
>> -
>>          ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>>                                                    &clip,
>> DRM_PLANE_HELPER_NO_SCALING,
>> @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
>> drm_plane *plane,
>>          if (ret)
>>                  return ret;
>>
>> +       if (!plane_state->visible || !crtc_state->enable)
>> +               return 0; /* nothing to check when disabling or disabled */
> if (!plane_state->visible) {
> 	WARN_ON(crtc_state->enabled);
> 	return 0;
> }
>
> The helper call above should guarantee this.
Yes, but I still see cases when crtc_state is NULL, thus
making crtc_state->enable to fail
>> +
>> +       if (plane_state->visible && crtc_state->enable)
> Similar here.
>
>> +               drm_mode_get_hv_timing(&crtc_state->mode,
>> +                                      &clip.x2, &clip.y2);
>> +
>>          if (!plane_state->visible)
>>                  return -EINVAL;
> This can now be removed, the plane helper takes care of checking for
> plane_state->visible != crtc_state->enable. Please also remove.
>
>>> We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>> anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
>>> case.
>> It doesn't look at it at the moment
>>> Otherwise we'll just go with your fix, but it feels all a bit too fragile,
>>> hence why I want to explore more robust options a bit.
>> At list with the change above it passes my test which failed
>> before. Although I cannot confirm it works for others, but it
>> certainly does for me.
>>> -Daniel
>> Do you want me to send v1 with the code above?
> Yes please, with my above cleanup suggestions.
Please see the patch under test attached (I believe it is what you mean,
with the only change that
     if (!plane_state->visible) {
         *if (crtc_state)*
             WARN_ON(crtc_state->enable);
         return 0;
     }
check is used).

Whith this patch + additional logs I have:

[   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1, 
DRM_IOCTL_MODE_ATOMIC
[...]
[   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
state 00000000c302cbbf to [NOCRTC]
[   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for 
plane state 00000000c302cbbf
[   18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7
[   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
[   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
[   18.940018] vdispl vdispl.0: [drm]   fb=0
[   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
[   18.940048] vdispl vdispl.0: [drm] 
src-pos=0.000000x0.000000+0.000000+0.000000
[   18.940067] vdispl vdispl.0: [drm]   rotation=1
[   18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
[   18.940226] ================================= plane_state->visible 0 
crtc_state           (null)
[...]
[   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
state 000000006bd50580 to [CRTC:30:crtc-0]
[   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for 
plane state 000000006bd50580
[   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set 
[MODE:1024x768] for CRTC state 00000000e5a28f6a
[   18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
[   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] mode changed
[   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] enable changed
[   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] active changed
[   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
Updating routing for [CONNECTOR:28:Virtual-1]
[   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
[   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] needs all connectors, enable: y, active: y
[   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all 
current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
[   18.980184] ================================= plane_state->visible 0 
crtc_state 00000000e5a28f6a
[   18.980205] crtc_state->enable 1

*[   19.022608] WARNING: CPU: 1 PID: 2105 at 
drivers/gpu/drm/drm_simple_kms_helper.c:137 
drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*

[...]

[   19.113601] ================================= plane_state->visible 0 
crtc_state 00000000e5a28f6a
[   19.113623] crtc_state->enable 1
[   19.113792] WARNING: CPU: 1 PID: 2105 at 
drivers/gpu/drm/drm_simple_kms_helper.c:137 
drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]

[...]

And finally

[   19.340249] ================================= plane_state->visible 0 
crtc_state 0000000036a1b1f5
[   19.340271] crtc_state->enable 0

So, it seems that crtc_state can still be NULL if 
"!plane_state->visible" making
NULL pointer dereference, so we need a check for that.
Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
always. So, probably we may want removing it.
>
> Thanks, Daniel
Thank you,
Oleksandr

[-- Attachment #2: 0001-drm-simple_kms_helper-Fix-NULL-pointer-dereference-w.patch --]
[-- Type: text/x-patch, Size: 1909 bytes --]

>From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Date: Tue, 13 Feb 2018 10:32:20 +0200
Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no
 active CRTC

It is possible that drm_simple_kms_plane_atomic_check called
with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
to 0 before doing any actual drawing. This leads to NULL pointer
dereference because in this case new CRTC state is NULL and must be
checked before accessing.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 9ca8a4a59b74..f54711ff9767 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
 	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
 						   &pipe->crtc);
-	if (!crtc_state->enable)
-		return 0; /* nothing to check when disabling or disabled */
-
-	if (crtc_state->enable)
-		drm_mode_get_hv_timing(&crtc_state->mode,
-				       &clip.x2, &clip.y2);
 
 	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
 						  &clip,
@@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 	if (ret)
 		return ret;
 
-	if (!plane_state->visible)
-		return -EINVAL;
+	if (!plane_state->visible) {
+		if (crtc_state)
+			WARN_ON(crtc_state->enable);
+		return 0;
+	}
+
+	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
 
 	if (!pipe->funcs || !pipe->funcs->check)
 		return 0;
-- 
2.7.4

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

[-- Attachment #1: Type: text/plain, Size: 8470 bytes --]

On 02/20/2018 01:17 PM, Daniel Vetter wrote:
> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>
>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>> dereference because in this case new CRTC state is NULL and must be
>>>> checked before accessing.
>>>>
>>>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>> ---
>>>>    drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>    	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>>>    	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>>    						   &pipe->crtc);
>>>> -	if (!crtc_state->enable)
>>>> -		return 0; /* nothing to check when disabling or disabled */
>>>> +
>>>> +	if (!crtc_state || !crtc_state->enable)
>>>> +		/* nothing to check when disabling or disabled or no CRTC set */
>>>> +		return 0;
>>>>    	if (crtc_state->enable)
>>>>    		drm_mode_get_hv_timing(&crtc_state->mode,
>>> Hm, this is a bit annoying, since the can_position = false parameter to
>>> drm_atomic_helper_check_plane_state is supposed to catch all this. Would
>>> moving all the checks after the call to that helper, and gating them on
>>> plane_state->visible also work?
>> Yes, it does work if this is what you mean:
> I wasn't sure, thanks for figuring this out!
>
>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>> index a05eca9cec8b..c48858bb2823 100644
>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>> @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
>> drm_plane *plane,
>>          crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>> &pipe->crtc);
>>
>> -       if (!crtc_state || !crtc_state->enable)
>> -               /* nothing to check when disabling or disabled or no CRTC
>> set */
>> -               return 0;
>> -
>> -       if (crtc_state->enable)
>> -               drm_mode_get_hv_timing(&crtc_state->mode,
>> -                                      &clip.x2, &clip.y2);
>> -
>>          ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>>                                                    &clip,
>> DRM_PLANE_HELPER_NO_SCALING,
>> @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
>> drm_plane *plane,
>>          if (ret)
>>                  return ret;
>>
>> +       if (!plane_state->visible || !crtc_state->enable)
>> +               return 0; /* nothing to check when disabling or disabled */
> if (!plane_state->visible) {
> 	WARN_ON(crtc_state->enabled);
> 	return 0;
> }
>
> The helper call above should guarantee this.
Yes, but I still see cases when crtc_state is NULL, thus
making crtc_state->enable to fail
>> +
>> +       if (plane_state->visible && crtc_state->enable)
> Similar here.
>
>> +               drm_mode_get_hv_timing(&crtc_state->mode,
>> +                                      &clip.x2, &clip.y2);
>> +
>>          if (!plane_state->visible)
>>                  return -EINVAL;
> This can now be removed, the plane helper takes care of checking for
> plane_state->visible != crtc_state->enable. Please also remove.
>
>>> We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>> anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
>>> case.
>> It doesn't look at it at the moment
>>> Otherwise we'll just go with your fix, but it feels all a bit too fragile,
>>> hence why I want to explore more robust options a bit.
>> At list with the change above it passes my test which failed
>> before. Although I cannot confirm it works for others, but it
>> certainly does for me.
>>> -Daniel
>> Do you want me to send v1 with the code above?
> Yes please, with my above cleanup suggestions.
Please see the patch under test attached (I believe it is what you mean,
with the only change that
     if (!plane_state->visible) {
         *if (crtc_state)*
             WARN_ON(crtc_state->enable);
         return 0;
     }
check is used).

Whith this patch + additional logs I have:

[   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1, 
DRM_IOCTL_MODE_ATOMIC
[...]
[   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
state 00000000c302cbbf to [NOCRTC]
[   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for 
plane state 00000000c302cbbf
[   18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7
[   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
[   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
[   18.940018] vdispl vdispl.0: [drm]   fb=0
[   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
[   18.940048] vdispl vdispl.0: [drm] 
src-pos=0.000000x0.000000+0.000000+0.000000
[   18.940067] vdispl vdispl.0: [drm]   rotation=1
[   18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
[   18.940226] ================================= plane_state->visible 0 
crtc_state           (null)
[...]
[   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
state 000000006bd50580 to [CRTC:30:crtc-0]
[   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for 
plane state 000000006bd50580
[   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set 
[MODE:1024x768] for CRTC state 00000000e5a28f6a
[   18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
[   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] mode changed
[   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] enable changed
[   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] active changed
[   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
Updating routing for [CONNECTOR:28:Virtual-1]
[   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
[   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] 
[CRTC:30:crtc-0] needs all connectors, enable: y, active: y
[   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all 
current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
[   18.980184] ================================= plane_state->visible 0 
crtc_state 00000000e5a28f6a
[   18.980205] crtc_state->enable 1

*[   19.022608] WARNING: CPU: 1 PID: 2105 at 
drivers/gpu/drm/drm_simple_kms_helper.c:137 
drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*

[...]

[   19.113601] ================================= plane_state->visible 0 
crtc_state 00000000e5a28f6a
[   19.113623] crtc_state->enable 1
[   19.113792] WARNING: CPU: 1 PID: 2105 at 
drivers/gpu/drm/drm_simple_kms_helper.c:137 
drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]

[...]

And finally

[   19.340249] ================================= plane_state->visible 0 
crtc_state 0000000036a1b1f5
[   19.340271] crtc_state->enable 0

So, it seems that crtc_state can still be NULL if 
"!plane_state->visible" making
NULL pointer dereference, so we need a check for that.
Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
always. So, probably we may want removing it.
>
> Thanks, Daniel
Thank you,
Oleksandr

[-- Attachment #2: 0001-drm-simple_kms_helper-Fix-NULL-pointer-dereference-w.patch --]
[-- Type: text/x-patch, Size: 1909 bytes --]

>From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Date: Tue, 13 Feb 2018 10:32:20 +0200
Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no
 active CRTC

It is possible that drm_simple_kms_plane_atomic_check called
with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
to 0 before doing any actual drawing. This leads to NULL pointer
dereference because in this case new CRTC state is NULL and must be
checked before accessing.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 9ca8a4a59b74..f54711ff9767 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
 	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
 						   &pipe->crtc);
-	if (!crtc_state->enable)
-		return 0; /* nothing to check when disabling or disabled */
-
-	if (crtc_state->enable)
-		drm_mode_get_hv_timing(&crtc_state->mode,
-				       &clip.x2, &clip.y2);
 
 	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
 						  &clip,
@@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 	if (ret)
 		return ret;
 
-	if (!plane_state->visible)
-		return -EINVAL;
+	if (!plane_state->visible) {
+		if (crtc_state)
+			WARN_ON(crtc_state->enable);
+		return 0;
+	}
+
+	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
 
 	if (!pipe->funcs || !pipe->funcs->check)
 		return 0;
-- 
2.7.4


[-- Attachment #3: Type: text/plain, Size: 160 bytes --]

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Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
> > On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
> > > On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> > > > On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
> > > > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > > > 
> > > > > It is possible that drm_simple_kms_plane_atomic_check called
> > > > > with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> > > > > to 0 before doing any actual drawing. This leads to NULL pointer
> > > > > dereference because in this case new CRTC state is NULL and must be
> > > > > checked before accessing.
> > > > > 
> > > > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > > > ---
> > > > >    drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
> > > > >    1 file changed, 4 insertions(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > index 9ca8a4a59b74..a05eca9cec8b 100644
> > > > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> > > > >    	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> > > > >    	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > > > >    						   &pipe->crtc);
> > > > > -	if (!crtc_state->enable)
> > > > > -		return 0; /* nothing to check when disabling or disabled */
> > > > > +
> > > > > +	if (!crtc_state || !crtc_state->enable)
> > > > > +		/* nothing to check when disabling or disabled or no CRTC set */
> > > > > +		return 0;
> > > > >    	if (crtc_state->enable)
> > > > >    		drm_mode_get_hv_timing(&crtc_state->mode,
> > > > Hm, this is a bit annoying, since the can_position = false parameter to
> > > > drm_atomic_helper_check_plane_state is supposed to catch all this. Would
> > > > moving all the checks after the call to that helper, and gating them on
> > > > plane_state->visible also work?
> > > Yes, it does work if this is what you mean:
> > I wasn't sure, thanks for figuring this out!
> > 
> > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > index a05eca9cec8b..c48858bb2823 100644
> > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
> > > drm_plane *plane,
> > >          crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > > &pipe->crtc);
> > > 
> > > -       if (!crtc_state || !crtc_state->enable)
> > > -               /* nothing to check when disabling or disabled or no CRTC
> > > set */
> > > -               return 0;
> > > -
> > > -       if (crtc_state->enable)
> > > -               drm_mode_get_hv_timing(&crtc_state->mode,
> > > -                                      &clip.x2, &clip.y2);
> > > -
> > >          ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
> > >                                                    &clip,
> > > DRM_PLANE_HELPER_NO_SCALING,
> > > @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
> > > drm_plane *plane,
> > >          if (ret)
> > >                  return ret;
> > > 
> > > +       if (!plane_state->visible || !crtc_state->enable)
> > > +               return 0; /* nothing to check when disabling or disabled */
> > if (!plane_state->visible) {
> > 	WARN_ON(crtc_state->enabled);
> > 	return 0;
> > }
> > 
> > The helper call above should guarantee this.
> Yes, but I still see cases when crtc_state is NULL, thus
> making crtc_state->enable to fail

Right, when the plane is completely off there's no CRTC state. Correct
check should be

	WARN_ON(crtc_state && crtc_state->enabled);


> > > +
> > > +       if (plane_state->visible && crtc_state->enable)
> > Similar here.
> > 
> > > +               drm_mode_get_hv_timing(&crtc_state->mode,
> > > +                                      &clip.x2, &clip.y2);
> > > +
> > >          if (!plane_state->visible)
> > >                  return -EINVAL;
> > This can now be removed, the plane helper takes care of checking for
> > plane_state->visible != crtc_state->enable. Please also remove.
> > 
> > > > We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
> > > > it can cope with crtc_state == NULL, but I think that's a good idea
> > > > anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
> > > > case.
> > > It doesn't look at it at the moment
> > > > Otherwise we'll just go with your fix, but it feels all a bit too fragile,
> > > > hence why I want to explore more robust options a bit.
> > > At list with the change above it passes my test which failed
> > > before. Although I cannot confirm it works for others, but it
> > > certainly does for me.
> > > > -Daniel
> > > Do you want me to send v1 with the code above?
> > Yes please, with my above cleanup suggestions.
> Please see the patch under test attached (I believe it is what you mean,
> with the only change that
>     if (!plane_state->visible) {
>         *if (crtc_state)*
>             WARN_ON(crtc_state->enable);
>         return 0;
>     }
> check is used).
> 
> Whith this patch + additional logs I have:
> 
> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
> DRM_IOCTL_MODE_ATOMIC
> [...]
> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
> 00000000c302cbbf to [NOCRTC]
> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for plane
> state 00000000c302cbbf
> [   18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7
> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
> [   18.940018] vdispl vdispl.0: [drm]   fb=0
> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
> [   18.940048] vdispl vdispl.0: [drm]
> src-pos=0.000000x0.000000+0.000000+0.000000
> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
> [   18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
> [   18.940226] ================================= plane_state->visible 0
> crtc_state           (null)
> [...]
> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
> 000000006bd50580 to [CRTC:30:crtc-0]
> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for plane
> state 000000006bd50580
> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
> [MODE:1024x768] for CRTC state 00000000e5a28f6a
> [   18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] mode changed
> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] enable changed
> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] active changed
> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> Updating routing for [CONNECTOR:28:Virtual-1]
> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all
> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
> [   18.980184] ================================= plane_state->visible 0
> crtc_state 00000000e5a28f6a
> [   18.980205] crtc_state->enable 1
> 
> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
> drivers/gpu/drm/drm_simple_kms_helper.c:137
> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
> 
> [...]
> 
> [   19.113601] ================================= plane_state->visible 0
> crtc_state 00000000e5a28f6a
> [   19.113623] crtc_state->enable 1
> [   19.113792] WARNING: CPU: 1 PID: 2105 at
> drivers/gpu/drm/drm_simple_kms_helper.c:137
> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
> 
> [...]
> 
> And finally
> 
> [   19.340249] ================================= plane_state->visible 0
> crtc_state 0000000036a1b1f5
> [   19.340271] crtc_state->enable 0
> 
> So, it seems that crtc_state can still be NULL if "!plane_state->visible"
> making
> NULL pointer dereference, so we need a check for that.
> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
> always. So, probably we may want removing it.
> > 
> > Thanks, Daniel
> Thank you,
> Oleksandr

> From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> Date: Tue, 13 Feb 2018 10:32:20 +0200
> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no
>  active CRTC
> 
> It is possible that drm_simple_kms_plane_atomic_check called
> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> to 0 before doing any actual drawing. This leads to NULL pointer
> dereference because in this case new CRTC state is NULL and must be
> checked before accessing.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 9ca8a4a59b74..f54711ff9767 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>  	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>  	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>  						   &pipe->crtc);
> -	if (!crtc_state->enable)
> -		return 0; /* nothing to check when disabling or disabled */
> -
> -	if (crtc_state->enable)
> -		drm_mode_get_hv_timing(&crtc_state->mode,
> -				       &clip.x2, &clip.y2);
>  
>  	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>  						  &clip,
> @@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>  	if (ret)
>  		return ret;
>  
> -	if (!plane_state->visible)
> -		return -EINVAL;
> +	if (!plane_state->visible) {
> +		if (crtc_state)
> +			WARN_ON(crtc_state->enable);
> +		return 0;
> +	}
> +
> +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);

lgtm. With or without the bikeshed to pull the crtc_state check into the
WARN_ON.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Please resubmit as a stand-alone patch, patchwork can't pull patches out
of attachments :-/
-Daniel

>  
>  	if (!pipe->funcs || !pipe->funcs->check)
>  		return 0;
> -- 
> 2.7.4
> 

> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
> > On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
> > > On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> > > > On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
> > > > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > > > 
> > > > > It is possible that drm_simple_kms_plane_atomic_check called
> > > > > with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> > > > > to 0 before doing any actual drawing. This leads to NULL pointer
> > > > > dereference because in this case new CRTC state is NULL and must be
> > > > > checked before accessing.
> > > > > 
> > > > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > > > ---
> > > > >    drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
> > > > >    1 file changed, 4 insertions(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > index 9ca8a4a59b74..a05eca9cec8b 100644
> > > > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> > > > >    	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> > > > >    	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > > > >    						   &pipe->crtc);
> > > > > -	if (!crtc_state->enable)
> > > > > -		return 0; /* nothing to check when disabling or disabled */
> > > > > +
> > > > > +	if (!crtc_state || !crtc_state->enable)
> > > > > +		/* nothing to check when disabling or disabled or no CRTC set */
> > > > > +		return 0;
> > > > >    	if (crtc_state->enable)
> > > > >    		drm_mode_get_hv_timing(&crtc_state->mode,
> > > > Hm, this is a bit annoying, since the can_position = false parameter to
> > > > drm_atomic_helper_check_plane_state is supposed to catch all this. Would
> > > > moving all the checks after the call to that helper, and gating them on
> > > > plane_state->visible also work?
> > > Yes, it does work if this is what you mean:
> > I wasn't sure, thanks for figuring this out!
> > 
> > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > index a05eca9cec8b..c48858bb2823 100644
> > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
> > > drm_plane *plane,
> > >          crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > > &pipe->crtc);
> > > 
> > > -       if (!crtc_state || !crtc_state->enable)
> > > -               /* nothing to check when disabling or disabled or no CRTC
> > > set */
> > > -               return 0;
> > > -
> > > -       if (crtc_state->enable)
> > > -               drm_mode_get_hv_timing(&crtc_state->mode,
> > > -                                      &clip.x2, &clip.y2);
> > > -
> > >          ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
> > >                                                    &clip,
> > > DRM_PLANE_HELPER_NO_SCALING,
> > > @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
> > > drm_plane *plane,
> > >          if (ret)
> > >                  return ret;
> > > 
> > > +       if (!plane_state->visible || !crtc_state->enable)
> > > +               return 0; /* nothing to check when disabling or disabled */
> > if (!plane_state->visible) {
> > 	WARN_ON(crtc_state->enabled);
> > 	return 0;
> > }
> > 
> > The helper call above should guarantee this.
> Yes, but I still see cases when crtc_state is NULL, thus
> making crtc_state->enable to fail

Right, when the plane is completely off there's no CRTC state. Correct
check should be

	WARN_ON(crtc_state && crtc_state->enabled);


> > > +
> > > +       if (plane_state->visible && crtc_state->enable)
> > Similar here.
> > 
> > > +               drm_mode_get_hv_timing(&crtc_state->mode,
> > > +                                      &clip.x2, &clip.y2);
> > > +
> > >          if (!plane_state->visible)
> > >                  return -EINVAL;
> > This can now be removed, the plane helper takes care of checking for
> > plane_state->visible != crtc_state->enable. Please also remove.
> > 
> > > > We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
> > > > it can cope with crtc_state == NULL, but I think that's a good idea
> > > > anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
> > > > case.
> > > It doesn't look at it at the moment
> > > > Otherwise we'll just go with your fix, but it feels all a bit too fragile,
> > > > hence why I want to explore more robust options a bit.
> > > At list with the change above it passes my test which failed
> > > before. Although I cannot confirm it works for others, but it
> > > certainly does for me.
> > > > -Daniel
> > > Do you want me to send v1 with the code above?
> > Yes please, with my above cleanup suggestions.
> Please see the patch under test attached (I believe it is what you mean,
> with the only change that
>     if (!plane_state->visible) {
>         *if (crtc_state)*
>             WARN_ON(crtc_state->enable);
>         return 0;
>     }
> check is used).
> 
> Whith this patch + additional logs I have:
> 
> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
> DRM_IOCTL_MODE_ATOMIC
> [...]
> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
> 00000000c302cbbf to [NOCRTC]
> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for plane
> state 00000000c302cbbf
> [   18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7
> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
> [   18.940018] vdispl vdispl.0: [drm]   fb=0
> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
> [   18.940048] vdispl vdispl.0: [drm]
> src-pos=0.000000x0.000000+0.000000+0.000000
> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
> [   18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
> [   18.940226] ================================= plane_state->visible 0
> crtc_state           (null)
> [...]
> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
> 000000006bd50580 to [CRTC:30:crtc-0]
> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for plane
> state 000000006bd50580
> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
> [MODE:1024x768] for CRTC state 00000000e5a28f6a
> [   18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] mode changed
> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] enable changed
> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] active changed
> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> Updating routing for [CONNECTOR:28:Virtual-1]
> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all
> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
> [   18.980184] ================================= plane_state->visible 0
> crtc_state 00000000e5a28f6a
> [   18.980205] crtc_state->enable 1
> 
> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
> drivers/gpu/drm/drm_simple_kms_helper.c:137
> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
> 
> [...]
> 
> [   19.113601] ================================= plane_state->visible 0
> crtc_state 00000000e5a28f6a
> [   19.113623] crtc_state->enable 1
> [   19.113792] WARNING: CPU: 1 PID: 2105 at
> drivers/gpu/drm/drm_simple_kms_helper.c:137
> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
> 
> [...]
> 
> And finally
> 
> [   19.340249] ================================= plane_state->visible 0
> crtc_state 0000000036a1b1f5
> [   19.340271] crtc_state->enable 0
> 
> So, it seems that crtc_state can still be NULL if "!plane_state->visible"
> making
> NULL pointer dereference, so we need a check for that.
> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
> always. So, probably we may want removing it.
> > 
> > Thanks, Daniel
> Thank you,
> Oleksandr

> From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> Date: Tue, 13 Feb 2018 10:32:20 +0200
> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no
>  active CRTC
> 
> It is possible that drm_simple_kms_plane_atomic_check called
> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> to 0 before doing any actual drawing. This leads to NULL pointer
> dereference because in this case new CRTC state is NULL and must be
> checked before accessing.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 9ca8a4a59b74..f54711ff9767 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>  	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>  	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>  						   &pipe->crtc);
> -	if (!crtc_state->enable)
> -		return 0; /* nothing to check when disabling or disabled */
> -
> -	if (crtc_state->enable)
> -		drm_mode_get_hv_timing(&crtc_state->mode,
> -				       &clip.x2, &clip.y2);
>  
>  	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>  						  &clip,
> @@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>  	if (ret)
>  		return ret;
>  
> -	if (!plane_state->visible)
> -		return -EINVAL;
> +	if (!plane_state->visible) {
> +		if (crtc_state)
> +			WARN_ON(crtc_state->enable);
> +		return 0;
> +	}
> +
> +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);

lgtm. With or without the bikeshed to pull the crtc_state check into the
WARN_ON.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Please resubmit as a stand-alone patch, patchwork can't pull patches out
of attachments :-/
-Daniel

>  
>  	if (!pipe->funcs || !pipe->funcs->check)
>  		return 0;
> -- 
> 2.7.4
> 

> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/20/2018 02:49 PM, Daniel Vetter wrote:
> On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
>> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
>>> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
>>>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
>>>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>>
>>>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>>>> dereference because in this case new CRTC state is NULL and must be
>>>>>> checked before accessing.
>>>>>>
>>>>>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>> ---
>>>>>>     drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>>>     1 file changed, 4 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>>>     	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>>>>>     	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>>     						   &pipe->crtc);
>>>>>> -	if (!crtc_state->enable)
>>>>>> -		return 0; /* nothing to check when disabling or disabled */
>>>>>> +
>>>>>> +	if (!crtc_state || !crtc_state->enable)
>>>>>> +		/* nothing to check when disabling or disabled or no CRTC set */
>>>>>> +		return 0;
>>>>>>     	if (crtc_state->enable)
>>>>>>     		drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> Hm, this is a bit annoying, since the can_position = false parameter to
>>>>> drm_atomic_helper_check_plane_state is supposed to catch all this. Would
>>>>> moving all the checks after the call to that helper, and gating them on
>>>>> plane_state->visible also work?
>>>> Yes, it does work if this is what you mean:
>>> I wasn't sure, thanks for figuring this out!
>>>
>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> index a05eca9cec8b..c48858bb2823 100644
>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
>>>> drm_plane *plane,
>>>>           crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>> &pipe->crtc);
>>>>
>>>> -       if (!crtc_state || !crtc_state->enable)
>>>> -               /* nothing to check when disabling or disabled or no CRTC
>>>> set */
>>>> -               return 0;
>>>> -
>>>> -       if (crtc_state->enable)
>>>> -               drm_mode_get_hv_timing(&crtc_state->mode,
>>>> -                                      &clip.x2, &clip.y2);
>>>> -
>>>>           ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>>>>                                                     &clip,
>>>> DRM_PLANE_HELPER_NO_SCALING,
>>>> @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
>>>> drm_plane *plane,
>>>>           if (ret)
>>>>                   return ret;
>>>>
>>>> +       if (!plane_state->visible || !crtc_state->enable)
>>>> +               return 0; /* nothing to check when disabling or disabled */
>>> if (!plane_state->visible) {
>>> 	WARN_ON(crtc_state->enabled);
>>> 	return 0;
>>> }
>>>
>>> The helper call above should guarantee this.
>> Yes, but I still see cases when crtc_state is NULL, thus
>> making crtc_state->enable to fail
> Right, when the plane is completely off there's no CRTC state. Correct
> check should be
>
> 	WARN_ON(crtc_state && crtc_state->enabled);
ok, will update with this additional check
>
>>>> +
>>>> +       if (plane_state->visible && crtc_state->enable)
>>> Similar here.
>>>
>>>> +               drm_mode_get_hv_timing(&crtc_state->mode,
>>>> +                                      &clip.x2, &clip.y2);
>>>> +
>>>>           if (!plane_state->visible)
>>>>                   return -EINVAL;
>>> This can now be removed, the plane helper takes care of checking for
>>> plane_state->visible != crtc_state->enable. Please also remove.
>>>
>>>>> We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
>>>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>>>> anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
>>>>> case.
>>>> It doesn't look at it at the moment
>>>>> Otherwise we'll just go with your fix, but it feels all a bit too fragile,
>>>>> hence why I want to explore more robust options a bit.
>>>> At list with the change above it passes my test which failed
>>>> before. Although I cannot confirm it works for others, but it
>>>> certainly does for me.
>>>>> -Daniel
>>>> Do you want me to send v1 with the code above?
>>> Yes please, with my above cleanup suggestions.
>> Please see the patch under test attached (I believe it is what you mean,
>> with the only change that
>>      if (!plane_state->visible) {
>>          *if (crtc_state)*
>>              WARN_ON(crtc_state->enable);
>>          return 0;
>>      }
>> check is used).
>>
>> Whith this patch + additional logs I have:
>>
>> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
>> DRM_IOCTL_MODE_ATOMIC
>> [...]
>> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
>> 00000000c302cbbf to [NOCRTC]
>> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for plane
>> state 00000000c302cbbf
>> [   18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7
>> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
>> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
>> [   18.940018] vdispl vdispl.0: [drm]   fb=0
>> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
>> [   18.940048] vdispl vdispl.0: [drm]
>> src-pos=0.000000x0.000000+0.000000+0.000000
>> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
>> [   18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
>> [   18.940226] ================================= plane_state->visible 0
>> crtc_state           (null)
>> [...]
>> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
>> 000000006bd50580 to [CRTC:30:crtc-0]
>> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for plane
>> state 000000006bd50580
>> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
>> [MODE:1024x768] for CRTC state 00000000e5a28f6a
>> [   18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
>> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] mode changed
>> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] enable changed
>> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] active changed
>> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> Updating routing for [CONNECTOR:28:Virtual-1]
>> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
>> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
>> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all
>> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
>> [   18.980184] ================================= plane_state->visible 0
>> crtc_state 00000000e5a28f6a
>> [   18.980205] crtc_state->enable 1
>>
>> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
>>
>> [...]
>>
>> [   19.113601] ================================= plane_state->visible 0
>> crtc_state 00000000e5a28f6a
>> [   19.113623] crtc_state->enable 1
>> [   19.113792] WARNING: CPU: 1 PID: 2105 at
>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
>>
>> [...]
>>
>> And finally
>>
>> [   19.340249] ================================= plane_state->visible 0
>> crtc_state 0000000036a1b1f5
>> [   19.340271] crtc_state->enable 0
>>
>> So, it seems that crtc_state can still be NULL if "!plane_state->visible"
>> making
>> NULL pointer dereference, so we need a check for that.
>> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
>> always. So, probably we may want removing it.
>>> Thanks, Daniel
>> Thank you,
>> Oleksandr
>>  From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> Date: Tue, 13 Feb 2018 10:32:20 +0200
>> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no
>>   active CRTC
>>
>> It is possible that drm_simple_kms_plane_atomic_check called
>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>> to 0 before doing any actual drawing. This leads to NULL pointer
>> dereference because in this case new CRTC state is NULL and must be
>> checked before accessing.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>>   1 file changed, 7 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>> index 9ca8a4a59b74..f54711ff9767 100644
>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>> @@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>   	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>   	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>   						   &pipe->crtc);
>> -	if (!crtc_state->enable)
>> -		return 0; /* nothing to check when disabling or disabled */
>> -
>> -	if (crtc_state->enable)
>> -		drm_mode_get_hv_timing(&crtc_state->mode,
>> -				       &clip.x2, &clip.y2);
>>   
>>   	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>>   						  &clip,
>> @@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>   	if (ret)
>>   		return ret;
>>   
>> -	if (!plane_state->visible)
>> -		return -EINVAL;
>> +	if (!plane_state->visible) {
>> +		if (crtc_state)
>> +			WARN_ON(crtc_state->enable);
>> +		return 0;
>> +	}
>> +
>> +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
> lgtm. With or without the bikeshed to pull the crtc_state check into the
> WARN_ON.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Thank you
>
> Please resubmit as a stand-alone patch, patchwork can't pull patches out
> of attachments :-/
oh, that was for demonstration purpose only, so we
are on the same page and see the patch we are discussing ;)
> -Daniel
>
>>   
>>   	if (!pipe->funcs || !pipe->funcs->check)
>>   		return 0;
>> -- 
>> 2.7.4
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/20/2018 02:49 PM, Daniel Vetter wrote:
> On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
>> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
>>> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko wrote:
>>>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko wrote:
>>>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>>
>>>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>>>> dereference because in this case new CRTC state is NULL and must be
>>>>>> checked before accessing.
>>>>>>
>>>>>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>> ---
>>>>>>     drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>>>     1 file changed, 4 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>> @@ -121,8 +121,10 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>>>     	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>>>>>     	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>>     						   &pipe->crtc);
>>>>>> -	if (!crtc_state->enable)
>>>>>> -		return 0; /* nothing to check when disabling or disabled */
>>>>>> +
>>>>>> +	if (!crtc_state || !crtc_state->enable)
>>>>>> +		/* nothing to check when disabling or disabled or no CRTC set */
>>>>>> +		return 0;
>>>>>>     	if (crtc_state->enable)
>>>>>>     		drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> Hm, this is a bit annoying, since the can_position = false parameter to
>>>>> drm_atomic_helper_check_plane_state is supposed to catch all this. Would
>>>>> moving all the checks after the call to that helper, and gating them on
>>>>> plane_state->visible also work?
>>>> Yes, it does work if this is what you mean:
>>> I wasn't sure, thanks for figuring this out!
>>>
>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> index a05eca9cec8b..c48858bb2823 100644
>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>> @@ -122,14 +122,6 @@ static int drm_simple_kms_plane_atomic_check(struct
>>>> drm_plane *plane,
>>>>           crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>> &pipe->crtc);
>>>>
>>>> -       if (!crtc_state || !crtc_state->enable)
>>>> -               /* nothing to check when disabling or disabled or no CRTC
>>>> set */
>>>> -               return 0;
>>>> -
>>>> -       if (crtc_state->enable)
>>>> -               drm_mode_get_hv_timing(&crtc_state->mode,
>>>> -                                      &clip.x2, &clip.y2);
>>>> -
>>>>           ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>>>>                                                     &clip,
>>>> DRM_PLANE_HELPER_NO_SCALING,
>>>> @@ -138,6 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct
>>>> drm_plane *plane,
>>>>           if (ret)
>>>>                   return ret;
>>>>
>>>> +       if (!plane_state->visible || !crtc_state->enable)
>>>> +               return 0; /* nothing to check when disabling or disabled */
>>> if (!plane_state->visible) {
>>> 	WARN_ON(crtc_state->enabled);
>>> 	return 0;
>>> }
>>>
>>> The helper call above should guarantee this.
>> Yes, but I still see cases when crtc_state is NULL, thus
>> making crtc_state->enable to fail
> Right, when the plane is completely off there's no CRTC state. Correct
> check should be
>
> 	WARN_ON(crtc_state && crtc_state->enabled);
ok, will update with this additional check
>
>>>> +
>>>> +       if (plane_state->visible && crtc_state->enable)
>>> Similar here.
>>>
>>>> +               drm_mode_get_hv_timing(&crtc_state->mode,
>>>> +                                      &clip.x2, &clip.y2);
>>>> +
>>>>           if (!plane_state->visible)
>>>>                   return -EINVAL;
>>> This can now be removed, the plane helper takes care of checking for
>>> plane_state->visible != crtc_state->enable. Please also remove.
>>>
>>>>> We'd need to add a guarantee to drm_atomic_helper_check_plane_state that
>>>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>>>> anyway. Atm it shouldn't end up looking at the crtc_state pointer in that
>>>>> case.
>>>> It doesn't look at it at the moment
>>>>> Otherwise we'll just go with your fix, but it feels all a bit too fragile,
>>>>> hence why I want to explore more robust options a bit.
>>>> At list with the change above it passes my test which failed
>>>> before. Although I cannot confirm it works for others, but it
>>>> certainly does for me.
>>>>> -Daniel
>>>> Do you want me to send v1 with the code above?
>>> Yes please, with my above cleanup suggestions.
>> Please see the patch under test attached (I believe it is what you mean,
>> with the only change that
>>      if (!plane_state->visible) {
>>          *if (crtc_state)*
>>              WARN_ON(crtc_state->enable);
>>          return 0;
>>      }
>> check is used).
>>
>> Whith this patch + additional logs I have:
>>
>> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
>> DRM_IOCTL_MODE_ATOMIC
>> [...]
>> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
>> 00000000c302cbbf to [NOCRTC]
>> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] for plane
>> state 00000000c302cbbf
>> [   18.939963] [drm:drm_atomic_print_state [drm]] checking 000000000bc224e7
>> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
>> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
>> [   18.940018] vdispl vdispl.0: [drm]   fb=0
>> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
>> [   18.940048] vdispl vdispl.0: [drm]
>> src-pos=0.000000x0.000000+0.000000+0.000000
>> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
>> [   18.940199] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
>> [   18.940226] ================================= plane_state->visible 0
>> crtc_state           (null)
>> [...]
>> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane state
>> 000000006bd50580 to [CRTC:30:crtc-0]
>> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] for plane
>> state 000000006bd50580
>> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
>> [MODE:1024x768] for CRTC state 00000000e5a28f6a
>> [   18.979425] [drm:drm_atomic_check_only [drm]] checking 000000000bc224e7
>> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] mode changed
>> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] enable changed
>> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] active changed
>> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> Updating routing for [CONNECTOR:28:Virtual-1]
>> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
>> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
>> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding all
>> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
>> [   18.980184] ================================= plane_state->visible 0
>> crtc_state 00000000e5a28f6a
>> [   18.980205] crtc_state->enable 1
>>
>> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
>>
>> [...]
>>
>> [   19.113601] ================================= plane_state->visible 0
>> crtc_state 00000000e5a28f6a
>> [   19.113623] crtc_state->enable 1
>> [   19.113792] WARNING: CPU: 1 PID: 2105 at
>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
>>
>> [...]
>>
>> And finally
>>
>> [   19.340249] ================================= plane_state->visible 0
>> crtc_state 0000000036a1b1f5
>> [   19.340271] crtc_state->enable 0
>>
>> So, it seems that crtc_state can still be NULL if "!plane_state->visible"
>> making
>> NULL pointer dereference, so we need a check for that.
>> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
>> always. So, probably we may want removing it.
>>> Thanks, Daniel
>> Thank you,
>> Oleksandr
>>  From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> Date: Tue, 13 Feb 2018 10:32:20 +0200
>> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no
>>   active CRTC
>>
>> It is possible that drm_simple_kms_plane_atomic_check called
>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>> to 0 before doing any actual drawing. This leads to NULL pointer
>> dereference because in this case new CRTC state is NULL and must be
>> checked before accessing.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>>   1 file changed, 7 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>> index 9ca8a4a59b74..f54711ff9767 100644
>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>> @@ -121,12 +121,6 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>   	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
>>   	crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>   						   &pipe->crtc);
>> -	if (!crtc_state->enable)
>> -		return 0; /* nothing to check when disabling or disabled */
>> -
>> -	if (crtc_state->enable)
>> -		drm_mode_get_hv_timing(&crtc_state->mode,
>> -				       &clip.x2, &clip.y2);
>>   
>>   	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>>   						  &clip,
>> @@ -136,8 +130,13 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>   	if (ret)
>>   		return ret;
>>   
>> -	if (!plane_state->visible)
>> -		return -EINVAL;
>> +	if (!plane_state->visible) {
>> +		if (crtc_state)
>> +			WARN_ON(crtc_state->enable);
>> +		return 0;
>> +	}
>> +
>> +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
> lgtm. With or without the bikeshed to pull the crtc_state check into the
> WARN_ON.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Thank you
>
> Please resubmit as a stand-alone patch, patchwork can't pull patches out
> of attachments :-/
oh, that was for demonstration purpose only, so we
are on the same page and see the patch we are discussing ;)
> -Daniel
>
>>   
>>   	if (!pipe->funcs || !pipe->funcs->check)
>>   		return 0;
>> -- 
>> 2.7.4
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

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Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/20/2018 02:53 PM, Oleksandr Andrushchenko wrote:
> On 02/20/2018 02:49 PM, Daniel Vetter wrote:
>> On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
>>> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
>>>> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko 
>>>> wrote:
>>>>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>>>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko 
>>>>>> wrote:
>>>>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>>>
>>>>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>>>>> with no CRTC set, e.g. when user-space application sets 
>>>>>>> CRTC_ID/FB_ID
>>>>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>>>>> dereference because in this case new CRTC state is NULL and must be
>>>>>>> checked before accessing.
>>>>>>>
>>>>>>> Signed-off-by: Oleksandr Andrushchenko 
>>>>>>> <oleksandr_andrushchenko@epam.com>
>>>>>>> ---
>>>>>>>     drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>>>>     1 file changed, 4 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c 
>>>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> @@ -121,8 +121,10 @@ static int 
>>>>>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>>>>         pipe = container_of(plane, struct 
>>>>>>> drm_simple_display_pipe, plane);
>>>>>>>         crtc_state = 
>>>>>>> drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>>>                                &pipe->crtc);
>>>>>>> -    if (!crtc_state->enable)
>>>>>>> -        return 0; /* nothing to check when disabling or 
>>>>>>> disabled */
>>>>>>> +
>>>>>>> +    if (!crtc_state || !crtc_state->enable)
>>>>>>> +        /* nothing to check when disabling or disabled or no 
>>>>>>> CRTC set */
>>>>>>> +        return 0;
>>>>>>>         if (crtc_state->enable)
>>>>>>> drm_mode_get_hv_timing(&crtc_state->mode,
>>>>>> Hm, this is a bit annoying, since the can_position = false 
>>>>>> parameter to
>>>>>> drm_atomic_helper_check_plane_state is supposed to catch all 
>>>>>> this. Would
>>>>>> moving all the checks after the call to that helper, and gating 
>>>>>> them on
>>>>>> plane_state->visible also work?
>>>>> Yes, it does work if this is what you mean:
>>>> I wasn't sure, thanks for figuring this out!
>>>>
>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> index a05eca9cec8b..c48858bb2823 100644
>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> @@ -122,14 +122,6 @@ static int 
>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>> drm_plane *plane,
>>>>>           crtc_state = 
>>>>> drm_atomic_get_new_crtc_state(plane_state->state,
>>>>> &pipe->crtc);
>>>>>
>>>>> -       if (!crtc_state || !crtc_state->enable)
>>>>> -               /* nothing to check when disabling or disabled or 
>>>>> no CRTC
>>>>> set */
>>>>> -               return 0;
>>>>> -
>>>>> -       if (crtc_state->enable)
>>>>> - drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> -                                      &clip.x2, &clip.y2);
>>>>> -
>>>>>           ret = drm_atomic_helper_check_plane_state(plane_state, 
>>>>> crtc_state,
>>>>> &clip,
>>>>> DRM_PLANE_HELPER_NO_SCALING,
>>>>> @@ -138,6 +130,13 @@ static int 
>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>> drm_plane *plane,
>>>>>           if (ret)
>>>>>                   return ret;
>>>>>
>>>>> +       if (!plane_state->visible || !crtc_state->enable)
>>>>> +               return 0; /* nothing to check when disabling or 
>>>>> disabled */
>>>> if (!plane_state->visible) {
>>>>     WARN_ON(crtc_state->enabled);
>>>>     return 0;
>>>> }
>>>>
>>>> The helper call above should guarantee this.
>>> Yes, but I still see cases when crtc_state is NULL, thus
>>> making crtc_state->enable to fail
>> Right, when the plane is completely off there's no CRTC state. Correct
>> check should be
>>
>>     WARN_ON(crtc_state && crtc_state->enabled);
> ok, will update with this additional check
huh, this indeed solves the NULL pointer dereference, but floods a lot
with every page flip I have, e.g. !plane_state->visible == true
and crtc_state is not NULL and crtc_state->enable == true,
thus firing WARN_ON.
Is this something wrong with my use-case/driver or it is still legal
to have such a configuration and leave it without WARN_ON and just
return 0?
>>
>>>>> +
>>>>> +       if (plane_state->visible && crtc_state->enable)
>>>> Similar here.
>>>>
>>>>> + drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> +                                      &clip.x2, &clip.y2);
>>>>> +
>>>>>           if (!plane_state->visible)
>>>>>                   return -EINVAL;
>>>> This can now be removed, the plane helper takes care of checking for
>>>> plane_state->visible != crtc_state->enable. Please also remove.
>>>>
>>>>>> We'd need to add a guarantee to 
>>>>>> drm_atomic_helper_check_plane_state that
>>>>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>>>>> anyway. Atm it shouldn't end up looking at the crtc_state pointer 
>>>>>> in that
>>>>>> case.
>>>>> It doesn't look at it at the moment
>>>>>> Otherwise we'll just go with your fix, but it feels all a bit too 
>>>>>> fragile,
>>>>>> hence why I want to explore more robust options a bit.
>>>>> At list with the change above it passes my test which failed
>>>>> before. Although I cannot confirm it works for others, but it
>>>>> certainly does for me.
>>>>>> -Daniel
>>>>> Do you want me to send v1 with the code above?
>>>> Yes please, with my above cleanup suggestions.
>>> Please see the patch under test attached (I believe it is what you 
>>> mean,
>>> with the only change that
>>>      if (!plane_state->visible) {
>>>          *if (crtc_state)*
>>>              WARN_ON(crtc_state->enable);
>>>          return 0;
>>>      }
>>> check is used).
>>>
>>> Whith this patch + additional logs I have:
>>>
>>> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
>>> DRM_IOCTL_MODE_ATOMIC
>>> [...]
>>> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
>>> state
>>> 00000000c302cbbf to [NOCRTC]
>>> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] 
>>> for plane
>>> state 00000000c302cbbf
>>> [   18.939963] [drm:drm_atomic_print_state [drm]] checking 
>>> 000000000bc224e7
>>> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
>>> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
>>> [   18.940018] vdispl vdispl.0: [drm]   fb=0
>>> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
>>> [   18.940048] vdispl vdispl.0: [drm]
>>> src-pos=0.000000x0.000000+0.000000+0.000000
>>> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
>>> [   18.940199] [drm:drm_atomic_check_only [drm]] checking 
>>> 000000000bc224e7
>>> [   18.940226] ================================= plane_state->visible 0
>>> crtc_state           (null)
>>> [...]
>>> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
>>> state
>>> 000000006bd50580 to [CRTC:30:crtc-0]
>>> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] 
>>> for plane
>>> state 000000006bd50580
>>> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
>>> [MODE:1024x768] for CRTC state 00000000e5a28f6a
>>> [   18.979425] [drm:drm_atomic_check_only [drm]] checking 
>>> 000000000bc224e7
>>> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] mode changed
>>> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] enable changed
>>> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] active changed
>>> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> Updating routing for [CONNECTOR:28:Virtual-1]
>>> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
>>> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
>>> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding 
>>> all
>>> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
>>> [   18.980184] ================================= plane_state->visible 0
>>> crtc_state 00000000e5a28f6a
>>> [   18.980205] crtc_state->enable 1
>>>
>>> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
>>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
>>>
>>> [...]
>>>
>>> [   19.113601] ================================= plane_state->visible 0
>>> crtc_state 00000000e5a28f6a
>>> [   19.113623] crtc_state->enable 1
>>> [   19.113792] WARNING: CPU: 1 PID: 2105 at
>>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
>>>
>>> [...]
>>>
>>> And finally
>>>
>>> [   19.340249] ================================= plane_state->visible 0
>>> crtc_state 0000000036a1b1f5
>>> [   19.340271] crtc_state->enable 0
>>>
>>> So, it seems that crtc_state can still be NULL if 
>>> "!plane_state->visible"
>>> making
>>> NULL pointer dereference, so we need a check for that.
>>> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
>>> always. So, probably we may want removing it.
>>>> Thanks, Daniel
>>> Thank you,
>>> Oleksandr
>>>  From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>> Date: Tue, 13 Feb 2018 10:32:20 +0200
>>> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference 
>>> with no
>>>   active CRTC
>>>
>>> It is possible that drm_simple_kms_plane_atomic_check called
>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>> dereference because in this case new CRTC state is NULL and must be
>>> checked before accessing.
>>>
>>> Signed-off-by: Oleksandr Andrushchenko 
>>> <oleksandr_andrushchenko@epam.com>
>>> ---
>>>   drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>>>   1 file changed, 7 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c 
>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>> index 9ca8a4a59b74..f54711ff9767 100644
>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>> @@ -121,12 +121,6 @@ static int 
>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>       pipe = container_of(plane, struct drm_simple_display_pipe, 
>>> plane);
>>>       crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>                              &pipe->crtc);
>>> -    if (!crtc_state->enable)
>>> -        return 0; /* nothing to check when disabling or disabled */
>>> -
>>> -    if (crtc_state->enable)
>>> -        drm_mode_get_hv_timing(&crtc_state->mode,
>>> -                       &clip.x2, &clip.y2);
>>>         ret = drm_atomic_helper_check_plane_state(plane_state, 
>>> crtc_state,
>>>                             &clip,
>>> @@ -136,8 +130,13 @@ static int 
>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>       if (ret)
>>>           return ret;
>>>   -    if (!plane_state->visible)
>>> -        return -EINVAL;
>>> +    if (!plane_state->visible) {
>>> +        if (crtc_state)
>>> +            WARN_ON(crtc_state->enable);
>>> +        return 0;
>>> +    }
>>> +
>>> +    drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
>> lgtm. With or without the bikeshed to pull the crtc_state check into the
>> WARN_ON.
>>
>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Thank you
>>
>> Please resubmit as a stand-alone patch, patchwork can't pull patches out
>> of attachments :-/
> oh, that was for demonstration purpose only, so we
> are on the same page and see the patch we are discussing ;)
>> -Daniel
>>
>>>         if (!pipe->funcs || !pipe->funcs->check)
>>>           return 0;
>>> -- 
>>> 2.7.4
>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/20/2018 02:53 PM, Oleksandr Andrushchenko wrote:
> On 02/20/2018 02:49 PM, Daniel Vetter wrote:
>> On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
>>> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
>>>> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr Andrushchenko 
>>>> wrote:
>>>>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>>>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr Andrushchenko 
>>>>>> wrote:
>>>>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>>>
>>>>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>>>>> with no CRTC set, e.g. when user-space application sets 
>>>>>>> CRTC_ID/FB_ID
>>>>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>>>>> dereference because in this case new CRTC state is NULL and must be
>>>>>>> checked before accessing.
>>>>>>>
>>>>>>> Signed-off-by: Oleksandr Andrushchenko 
>>>>>>> <oleksandr_andrushchenko@epam.com>
>>>>>>> ---
>>>>>>>     drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>>>>     1 file changed, 4 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c 
>>>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> @@ -121,8 +121,10 @@ static int 
>>>>>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>>>>         pipe = container_of(plane, struct 
>>>>>>> drm_simple_display_pipe, plane);
>>>>>>>         crtc_state = 
>>>>>>> drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>>>                                &pipe->crtc);
>>>>>>> -    if (!crtc_state->enable)
>>>>>>> -        return 0; /* nothing to check when disabling or 
>>>>>>> disabled */
>>>>>>> +
>>>>>>> +    if (!crtc_state || !crtc_state->enable)
>>>>>>> +        /* nothing to check when disabling or disabled or no 
>>>>>>> CRTC set */
>>>>>>> +        return 0;
>>>>>>>         if (crtc_state->enable)
>>>>>>> drm_mode_get_hv_timing(&crtc_state->mode,
>>>>>> Hm, this is a bit annoying, since the can_position = false 
>>>>>> parameter to
>>>>>> drm_atomic_helper_check_plane_state is supposed to catch all 
>>>>>> this. Would
>>>>>> moving all the checks after the call to that helper, and gating 
>>>>>> them on
>>>>>> plane_state->visible also work?
>>>>> Yes, it does work if this is what you mean:
>>>> I wasn't sure, thanks for figuring this out!
>>>>
>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> index a05eca9cec8b..c48858bb2823 100644
>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> @@ -122,14 +122,6 @@ static int 
>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>> drm_plane *plane,
>>>>>           crtc_state = 
>>>>> drm_atomic_get_new_crtc_state(plane_state->state,
>>>>> &pipe->crtc);
>>>>>
>>>>> -       if (!crtc_state || !crtc_state->enable)
>>>>> -               /* nothing to check when disabling or disabled or 
>>>>> no CRTC
>>>>> set */
>>>>> -               return 0;
>>>>> -
>>>>> -       if (crtc_state->enable)
>>>>> - drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> -                                      &clip.x2, &clip.y2);
>>>>> -
>>>>>           ret = drm_atomic_helper_check_plane_state(plane_state, 
>>>>> crtc_state,
>>>>> &clip,
>>>>> DRM_PLANE_HELPER_NO_SCALING,
>>>>> @@ -138,6 +130,13 @@ static int 
>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>> drm_plane *plane,
>>>>>           if (ret)
>>>>>                   return ret;
>>>>>
>>>>> +       if (!plane_state->visible || !crtc_state->enable)
>>>>> +               return 0; /* nothing to check when disabling or 
>>>>> disabled */
>>>> if (!plane_state->visible) {
>>>>     WARN_ON(crtc_state->enabled);
>>>>     return 0;
>>>> }
>>>>
>>>> The helper call above should guarantee this.
>>> Yes, but I still see cases when crtc_state is NULL, thus
>>> making crtc_state->enable to fail
>> Right, when the plane is completely off there's no CRTC state. Correct
>> check should be
>>
>>     WARN_ON(crtc_state && crtc_state->enabled);
> ok, will update with this additional check
huh, this indeed solves the NULL pointer dereference, but floods a lot
with every page flip I have, e.g. !plane_state->visible == true
and crtc_state is not NULL and crtc_state->enable == true,
thus firing WARN_ON.
Is this something wrong with my use-case/driver or it is still legal
to have such a configuration and leave it without WARN_ON and just
return 0?
>>
>>>>> +
>>>>> +       if (plane_state->visible && crtc_state->enable)
>>>> Similar here.
>>>>
>>>>> + drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> +                                      &clip.x2, &clip.y2);
>>>>> +
>>>>>           if (!plane_state->visible)
>>>>>                   return -EINVAL;
>>>> This can now be removed, the plane helper takes care of checking for
>>>> plane_state->visible != crtc_state->enable. Please also remove.
>>>>
>>>>>> We'd need to add a guarantee to 
>>>>>> drm_atomic_helper_check_plane_state that
>>>>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>>>>> anyway. Atm it shouldn't end up looking at the crtc_state pointer 
>>>>>> in that
>>>>>> case.
>>>>> It doesn't look at it at the moment
>>>>>> Otherwise we'll just go with your fix, but it feels all a bit too 
>>>>>> fragile,
>>>>>> hence why I want to explore more robust options a bit.
>>>>> At list with the change above it passes my test which failed
>>>>> before. Although I cannot confirm it works for others, but it
>>>>> certainly does for me.
>>>>>> -Daniel
>>>>> Do you want me to send v1 with the code above?
>>>> Yes please, with my above cleanup suggestions.
>>> Please see the patch under test attached (I believe it is what you 
>>> mean,
>>> with the only change that
>>>      if (!plane_state->visible) {
>>>          *if (crtc_state)*
>>>              WARN_ON(crtc_state->enable);
>>>          return 0;
>>>      }
>>> check is used).
>>>
>>> Whith this patch + additional logs I have:
>>>
>>> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
>>> DRM_IOCTL_MODE_ATOMIC
>>> [...]
>>> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
>>> state
>>> 00000000c302cbbf to [NOCRTC]
>>> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set [NOFB] 
>>> for plane
>>> state 00000000c302cbbf
>>> [   18.939963] [drm:drm_atomic_print_state [drm]] checking 
>>> 000000000bc224e7
>>> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
>>> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
>>> [   18.940018] vdispl vdispl.0: [drm]   fb=0
>>> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
>>> [   18.940048] vdispl vdispl.0: [drm]
>>> src-pos=0.000000x0.000000+0.000000+0.000000
>>> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
>>> [   18.940199] [drm:drm_atomic_check_only [drm]] checking 
>>> 000000000bc224e7
>>> [   18.940226] ================================= plane_state->visible 0
>>> crtc_state           (null)
>>> [...]
>>> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link plane 
>>> state
>>> 000000006bd50580 to [CRTC:30:crtc-0]
>>> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set [FB:35] 
>>> for plane
>>> state 000000006bd50580
>>> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
>>> [MODE:1024x768] for CRTC state 00000000e5a28f6a
>>> [   18.979425] [drm:drm_atomic_check_only [drm]] checking 
>>> 000000000bc224e7
>>> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] mode changed
>>> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] enable changed
>>> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] active changed
>>> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> Updating routing for [CONNECTOR:28:Virtual-1]
>>> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
>>> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
>>> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]] Adding 
>>> all
>>> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
>>> [   18.980184] ================================= plane_state->visible 0
>>> crtc_state 00000000e5a28f6a
>>> [   18.980205] crtc_state->enable 1
>>>
>>> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
>>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
>>>
>>> [...]
>>>
>>> [   19.113601] ================================= plane_state->visible 0
>>> crtc_state 00000000e5a28f6a
>>> [   19.113623] crtc_state->enable 1
>>> [   19.113792] WARNING: CPU: 1 PID: 2105 at
>>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
>>>
>>> [...]
>>>
>>> And finally
>>>
>>> [   19.340249] ================================= plane_state->visible 0
>>> crtc_state 0000000036a1b1f5
>>> [   19.340271] crtc_state->enable 0
>>>
>>> So, it seems that crtc_state can still be NULL if 
>>> "!plane_state->visible"
>>> making
>>> NULL pointer dereference, so we need a check for that.
>>> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
>>> always. So, probably we may want removing it.
>>>> Thanks, Daniel
>>> Thank you,
>>> Oleksandr
>>>  From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>> Date: Tue, 13 Feb 2018 10:32:20 +0200
>>> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference 
>>> with no
>>>   active CRTC
>>>
>>> It is possible that drm_simple_kms_plane_atomic_check called
>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>> dereference because in this case new CRTC state is NULL and must be
>>> checked before accessing.
>>>
>>> Signed-off-by: Oleksandr Andrushchenko 
>>> <oleksandr_andrushchenko@epam.com>
>>> ---
>>>   drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>>>   1 file changed, 7 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c 
>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>> index 9ca8a4a59b74..f54711ff9767 100644
>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>> @@ -121,12 +121,6 @@ static int 
>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>       pipe = container_of(plane, struct drm_simple_display_pipe, 
>>> plane);
>>>       crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>                              &pipe->crtc);
>>> -    if (!crtc_state->enable)
>>> -        return 0; /* nothing to check when disabling or disabled */
>>> -
>>> -    if (crtc_state->enable)
>>> -        drm_mode_get_hv_timing(&crtc_state->mode,
>>> -                       &clip.x2, &clip.y2);
>>>         ret = drm_atomic_helper_check_plane_state(plane_state, 
>>> crtc_state,
>>>                             &clip,
>>> @@ -136,8 +130,13 @@ static int 
>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>       if (ret)
>>>           return ret;
>>>   -    if (!plane_state->visible)
>>> -        return -EINVAL;
>>> +    if (!plane_state->visible) {
>>> +        if (crtc_state)
>>> +            WARN_ON(crtc_state->enable);
>>> +        return 0;
>>> +    }
>>> +
>>> +    drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
>> lgtm. With or without the bikeshed to pull the crtc_state check into the
>> WARN_ON.
>>
>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Thank you
>>
>> Please resubmit as a stand-alone patch, patchwork can't pull patches out
>> of attachments :-/
> oh, that was for demonstration purpose only, so we
> are on the same page and see the patch we are discussing ;)
>> -Daniel
>>
>>>         if (!pipe->funcs || !pipe->funcs->check)
>>>           return 0;
>>> -- 
>>> 2.7.4
>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>

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Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Tue, Feb 20, 2018 at 03:29:07PM +0200, Oleksandr Andrushchenko wrote:
> On 02/20/2018 02:53 PM, Oleksandr Andrushchenko wrote:
> > On 02/20/2018 02:49 PM, Daniel Vetter wrote:
> > > On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
> > > > On 02/20/2018 01:17 PM, Daniel Vetter wrote:
> > > > > On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr
> > > > > Andrushchenko wrote:
> > > > > > On 02/19/2018 04:30 PM, Daniel Vetter wrote:
> > > > > > > On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr
> > > > > > > Andrushchenko wrote:
> > > > > > > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > > > > > > 
> > > > > > > > It is possible that drm_simple_kms_plane_atomic_check called
> > > > > > > > with no CRTC set, e.g. when user-space
> > > > > > > > application sets CRTC_ID/FB_ID
> > > > > > > > to 0 before doing any actual drawing. This leads to NULL pointer
> > > > > > > > dereference because in this case new CRTC state is NULL and must be
> > > > > > > > checked before accessing.
> > > > > > > > 
> > > > > > > > Signed-off-by: Oleksandr Andrushchenko
> > > > > > > > <oleksandr_andrushchenko@epam.com>
> > > > > > > > ---
> > > > > > > >     drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
> > > > > > > >     1 file changed, 4 insertions(+), 2 deletions(-)
> > > > > > > > 
> > > > > > > > diff --git
> > > > > > > > a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > > > b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > > > index 9ca8a4a59b74..a05eca9cec8b 100644
> > > > > > > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > > > @@ -121,8 +121,10 @@ static int
> > > > > > > > drm_simple_kms_plane_atomic_check(struct
> > > > > > > > drm_plane *plane,
> > > > > > > >         pipe = container_of(plane, struct
> > > > > > > > drm_simple_display_pipe, plane);
> > > > > > > >         crtc_state =
> > > > > > > > drm_atomic_get_new_crtc_state(plane_state->state,
> > > > > > > >                                &pipe->crtc);
> > > > > > > > -    if (!crtc_state->enable)
> > > > > > > > -        return 0; /* nothing to check when
> > > > > > > > disabling or disabled */
> > > > > > > > +
> > > > > > > > +    if (!crtc_state || !crtc_state->enable)
> > > > > > > > +        /* nothing to check when disabling or
> > > > > > > > disabled or no CRTC set */
> > > > > > > > +        return 0;
> > > > > > > >         if (crtc_state->enable)
> > > > > > > > drm_mode_get_hv_timing(&crtc_state->mode,
> > > > > > > Hm, this is a bit annoying, since the can_position =
> > > > > > > false parameter to
> > > > > > > drm_atomic_helper_check_plane_state is supposed to
> > > > > > > catch all this. Would
> > > > > > > moving all the checks after the call to that helper,
> > > > > > > and gating them on
> > > > > > > plane_state->visible also work?
> > > > > > Yes, it does work if this is what you mean:
> > > > > I wasn't sure, thanks for figuring this out!
> > > > > 
> > > > > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > index a05eca9cec8b..c48858bb2823 100644
> > > > > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > > > @@ -122,14 +122,6 @@ static int
> > > > > > drm_simple_kms_plane_atomic_check(struct
> > > > > > drm_plane *plane,
> > > > > >           crtc_state =
> > > > > > drm_atomic_get_new_crtc_state(plane_state->state,
> > > > > > &pipe->crtc);
> > > > > > 
> > > > > > -       if (!crtc_state || !crtc_state->enable)
> > > > > > -               /* nothing to check when disabling or
> > > > > > disabled or no CRTC
> > > > > > set */
> > > > > > -               return 0;
> > > > > > -
> > > > > > -       if (crtc_state->enable)
> > > > > > - drm_mode_get_hv_timing(&crtc_state->mode,
> > > > > > -                                      &clip.x2, &clip.y2);
> > > > > > -
> > > > > >           ret =
> > > > > > drm_atomic_helper_check_plane_state(plane_state,
> > > > > > crtc_state,
> > > > > > &clip,
> > > > > > DRM_PLANE_HELPER_NO_SCALING,
> > > > > > @@ -138,6 +130,13 @@ static int
> > > > > > drm_simple_kms_plane_atomic_check(struct
> > > > > > drm_plane *plane,
> > > > > >           if (ret)
> > > > > >                   return ret;
> > > > > > 
> > > > > > +       if (!plane_state->visible || !crtc_state->enable)
> > > > > > +               return 0; /* nothing to check when
> > > > > > disabling or disabled */
> > > > > if (!plane_state->visible) {
> > > > >     WARN_ON(crtc_state->enabled);
> > > > >     return 0;
> > > > > }
> > > > > 
> > > > > The helper call above should guarantee this.
> > > > Yes, but I still see cases when crtc_state is NULL, thus
> > > > making crtc_state->enable to fail
> > > Right, when the plane is completely off there's no CRTC state. Correct
> > > check should be
> > > 
> > >     WARN_ON(crtc_state && crtc_state->enabled);
> > ok, will update with this additional check
> huh, this indeed solves the NULL pointer dereference, but floods a lot
> with every page flip I have, e.g. !plane_state->visible == true
> and crtc_state is not NULL and crtc_state->enable == true,
> thus firing WARN_ON.
> Is this something wrong with my use-case/driver or it is still legal
> to have such a configuration and leave it without WARN_ON and just
> return 0?

1 week of vacation later I have to admit that this WARN_ON is completely
bogus :-)

Sorry for all the confusion, pls leave it out.
-Daniel

> > > 
> > > > > > +
> > > > > > +       if (plane_state->visible && crtc_state->enable)
> > > > > Similar here.
> > > > > 
> > > > > > + drm_mode_get_hv_timing(&crtc_state->mode,
> > > > > > +                                      &clip.x2, &clip.y2);
> > > > > > +
> > > > > >           if (!plane_state->visible)
> > > > > >                   return -EINVAL;
> > > > > This can now be removed, the plane helper takes care of checking for
> > > > > plane_state->visible != crtc_state->enable. Please also remove.
> > > > > 
> > > > > > > We'd need to add a guarantee to
> > > > > > > drm_atomic_helper_check_plane_state that
> > > > > > > it can cope with crtc_state == NULL, but I think that's a good idea
> > > > > > > anyway. Atm it shouldn't end up looking at the
> > > > > > > crtc_state pointer in that
> > > > > > > case.
> > > > > > It doesn't look at it at the moment
> > > > > > > Otherwise we'll just go with your fix, but it feels
> > > > > > > all a bit too fragile,
> > > > > > > hence why I want to explore more robust options a bit.
> > > > > > At list with the change above it passes my test which failed
> > > > > > before. Although I cannot confirm it works for others, but it
> > > > > > certainly does for me.
> > > > > > > -Daniel
> > > > > > Do you want me to send v1 with the code above?
> > > > > Yes please, with my above cleanup suggestions.
> > > > Please see the patch under test attached (I believe it is what
> > > > you mean,
> > > > with the only change that
> > > >      if (!plane_state->visible) {
> > > >          *if (crtc_state)*
> > > >              WARN_ON(crtc_state->enable);
> > > >          return 0;
> > > >      }
> > > > check is used).
> > > > 
> > > > Whith this patch + additional logs I have:
> > > > 
> > > > [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
> > > > DRM_IOCTL_MODE_ATOMIC
> > > > [...]
> > > > [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link
> > > > plane state
> > > > 00000000c302cbbf to [NOCRTC]
> > > > [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set
> > > > [NOFB] for plane
> > > > state 00000000c302cbbf
> > > > [   18.939963] [drm:drm_atomic_print_state [drm]] checking
> > > > 000000000bc224e7
> > > > [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
> > > > [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
> > > > [   18.940018] vdispl vdispl.0: [drm]   fb=0
> > > > [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
> > > > [   18.940048] vdispl vdispl.0: [drm]
> > > > src-pos=0.000000x0.000000+0.000000+0.000000
> > > > [   18.940067] vdispl vdispl.0: [drm]   rotation=1
> > > > [   18.940199] [drm:drm_atomic_check_only [drm]] checking
> > > > 000000000bc224e7
> > > > [   18.940226] ================================= plane_state->visible 0
> > > > crtc_state           (null)
> > > > [...]
> > > > [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link
> > > > plane state
> > > > 000000006bd50580 to [CRTC:30:crtc-0]
> > > > [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set
> > > > [FB:35] for plane
> > > > state 000000006bd50580
> > > > [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
> > > > [MODE:1024x768] for CRTC state 00000000e5a28f6a
> > > > [   18.979425] [drm:drm_atomic_check_only [drm]] checking
> > > > 000000000bc224e7
> > > > [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> > > > [CRTC:30:crtc-0] mode changed
> > > > [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> > > > [CRTC:30:crtc-0] enable changed
> > > > [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> > > > [CRTC:30:crtc-0] active changed
> > > > [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> > > > Updating routing for [CONNECTOR:28:Virtual-1]
> > > > [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> > > > [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
> > > > [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
> > > > [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
> > > > [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]]
> > > > Adding all
> > > > current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
> > > > [   18.980184] ================================= plane_state->visible 0
> > > > crtc_state 00000000e5a28f6a
> > > > [   18.980205] crtc_state->enable 1
> > > > 
> > > > *[   19.022608] WARNING: CPU: 1 PID: 2105 at
> > > > drivers/gpu/drm/drm_simple_kms_helper.c:137
> > > > drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
> > > > 
> > > > [...]
> > > > 
> > > > [   19.113601] ================================= plane_state->visible 0
> > > > crtc_state 00000000e5a28f6a
> > > > [   19.113623] crtc_state->enable 1
> > > > [   19.113792] WARNING: CPU: 1 PID: 2105 at
> > > > drivers/gpu/drm/drm_simple_kms_helper.c:137
> > > > drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
> > > > 
> > > > [...]
> > > > 
> > > > And finally
> > > > 
> > > > [   19.340249] ================================= plane_state->visible 0
> > > > crtc_state 0000000036a1b1f5
> > > > [   19.340271] crtc_state->enable 0
> > > > 
> > > > So, it seems that crtc_state can still be NULL if
> > > > "!plane_state->visible"
> > > > making
> > > > NULL pointer dereference, so we need a check for that.
> > > > Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
> > > > always. So, probably we may want removing it.
> > > > > Thanks, Daniel
> > > > Thank you,
> > > > Oleksandr
> > > >  From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
> > > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> > > > Date: Tue, 13 Feb 2018 10:32:20 +0200
> > > > Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer
> > > > dereference with no
> > > >   active CRTC
> > > > 
> > > > It is possible that drm_simple_kms_plane_atomic_check called
> > > > with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
> > > > to 0 before doing any actual drawing. This leads to NULL pointer
> > > > dereference because in this case new CRTC state is NULL and must be
> > > > checked before accessing.
> > > > 
> > > > Signed-off-by: Oleksandr Andrushchenko
> > > > <oleksandr_andrushchenko@epam.com>
> > > > ---
> > > >   drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
> > > >   1 file changed, 7 insertions(+), 8 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > index 9ca8a4a59b74..f54711ff9767 100644
> > > > --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> > > > @@ -121,12 +121,6 @@ static int
> > > > drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> > > >       pipe = container_of(plane, struct drm_simple_display_pipe,
> > > > plane);
> > > >       crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
> > > >                              &pipe->crtc);
> > > > -    if (!crtc_state->enable)
> > > > -        return 0; /* nothing to check when disabling or disabled */
> > > > -
> > > > -    if (crtc_state->enable)
> > > > -        drm_mode_get_hv_timing(&crtc_state->mode,
> > > > -                       &clip.x2, &clip.y2);
> > > >         ret = drm_atomic_helper_check_plane_state(plane_state,
> > > > crtc_state,
> > > >                             &clip,
> > > > @@ -136,8 +130,13 @@ static int
> > > > drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> > > >       if (ret)
> > > >           return ret;
> > > >   -    if (!plane_state->visible)
> > > > -        return -EINVAL;
> > > > +    if (!plane_state->visible) {
> > > > +        if (crtc_state)
> > > > +            WARN_ON(crtc_state->enable);
> > > > +        return 0;
> > > > +    }
> > > > +
> > > > +    drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
> > > lgtm. With or without the bikeshed to pull the crtc_state check into the
> > > WARN_ON.
> > > 
> > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Thank you
> > > 
> > > Please resubmit as a stand-alone patch, patchwork can't pull patches out
> > > of attachments :-/
> > oh, that was for demonstration purpose only, so we
> > are on the same page and see the patch we are discussing ;)
> > > -Daniel
> > > 
> > > >         if (!pipe->funcs || !pipe->funcs->check)
> > > >           return 0;
> > > > -- 
> > > > 2.7.4
> > > > 
> > > > _______________________________________________
> > > > dri-devel mailing list
> > > > dri-devel@lists.freedesktop.org
> > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > > 
> > 
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 03/05/2018 10:52 AM, Daniel Vetter wrote:
> On Tue, Feb 20, 2018 at 03:29:07PM +0200, Oleksandr Andrushchenko wrote:
>> On 02/20/2018 02:53 PM, Oleksandr Andrushchenko wrote:
>>> On 02/20/2018 02:49 PM, Daniel Vetter wrote:
>>>> On Tue, Feb 20, 2018 at 02:36:05PM +0200, Oleksandr Andrushchenko wrote:
>>>>> On 02/20/2018 01:17 PM, Daniel Vetter wrote:
>>>>>> On Mon, Feb 19, 2018 at 04:58:43PM +0200, Oleksandr
>>>>>> Andrushchenko wrote:
>>>>>>> On 02/19/2018 04:30 PM, Daniel Vetter wrote:
>>>>>>>> On Tue, Feb 13, 2018 at 10:44:16AM +0200, Oleksandr
>>>>>>>> Andrushchenko wrote:
>>>>>>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>>>>>>
>>>>>>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>>>>>>> with no CRTC set, e.g. when user-space
>>>>>>>>> application sets CRTC_ID/FB_ID
>>>>>>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>>>>>>> dereference because in this case new CRTC state is NULL and must be
>>>>>>>>> checked before accessing.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Oleksandr Andrushchenko
>>>>>>>>> <oleksandr_andrushchenko@epam.com>
>>>>>>>>> ---
>>>>>>>>>      drivers/gpu/drm/drm_simple_kms_helper.c | 6 ++++--
>>>>>>>>>      1 file changed, 4 insertions(+), 2 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git
>>>>>>>>> a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> index 9ca8a4a59b74..a05eca9cec8b 100644
>>>>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>>>> @@ -121,8 +121,10 @@ static int
>>>>>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>>>>>> drm_plane *plane,
>>>>>>>>>          pipe = container_of(plane, struct
>>>>>>>>> drm_simple_display_pipe, plane);
>>>>>>>>>          crtc_state =
>>>>>>>>> drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>>>>>                                 &pipe->crtc);
>>>>>>>>> -    if (!crtc_state->enable)
>>>>>>>>> -        return 0; /* nothing to check when
>>>>>>>>> disabling or disabled */
>>>>>>>>> +
>>>>>>>>> +    if (!crtc_state || !crtc_state->enable)
>>>>>>>>> +        /* nothing to check when disabling or
>>>>>>>>> disabled or no CRTC set */
>>>>>>>>> +        return 0;
>>>>>>>>>          if (crtc_state->enable)
>>>>>>>>> drm_mode_get_hv_timing(&crtc_state->mode,
>>>>>>>> Hm, this is a bit annoying, since the can_position =
>>>>>>>> false parameter to
>>>>>>>> drm_atomic_helper_check_plane_state is supposed to
>>>>>>>> catch all this. Would
>>>>>>>> moving all the checks after the call to that helper,
>>>>>>>> and gating them on
>>>>>>>> plane_state->visible also work?
>>>>>>> Yes, it does work if this is what you mean:
>>>>>> I wasn't sure, thanks for figuring this out!
>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> index a05eca9cec8b..c48858bb2823 100644
>>>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>>>> @@ -122,14 +122,6 @@ static int
>>>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>>>> drm_plane *plane,
>>>>>>>            crtc_state =
>>>>>>> drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>>> &pipe->crtc);
>>>>>>>
>>>>>>> -       if (!crtc_state || !crtc_state->enable)
>>>>>>> -               /* nothing to check when disabling or
>>>>>>> disabled or no CRTC
>>>>>>> set */
>>>>>>> -               return 0;
>>>>>>> -
>>>>>>> -       if (crtc_state->enable)
>>>>>>> - drm_mode_get_hv_timing(&crtc_state->mode,
>>>>>>> -                                      &clip.x2, &clip.y2);
>>>>>>> -
>>>>>>>            ret =
>>>>>>> drm_atomic_helper_check_plane_state(plane_state,
>>>>>>> crtc_state,
>>>>>>> &clip,
>>>>>>> DRM_PLANE_HELPER_NO_SCALING,
>>>>>>> @@ -138,6 +130,13 @@ static int
>>>>>>> drm_simple_kms_plane_atomic_check(struct
>>>>>>> drm_plane *plane,
>>>>>>>            if (ret)
>>>>>>>                    return ret;
>>>>>>>
>>>>>>> +       if (!plane_state->visible || !crtc_state->enable)
>>>>>>> +               return 0; /* nothing to check when
>>>>>>> disabling or disabled */
>>>>>> if (!plane_state->visible) {
>>>>>>      WARN_ON(crtc_state->enabled);
>>>>>>      return 0;
>>>>>> }
>>>>>>
>>>>>> The helper call above should guarantee this.
>>>>> Yes, but I still see cases when crtc_state is NULL, thus
>>>>> making crtc_state->enable to fail
>>>> Right, when the plane is completely off there's no CRTC state. Correct
>>>> check should be
>>>>
>>>>      WARN_ON(crtc_state && crtc_state->enabled);
>>> ok, will update with this additional check
>> huh, this indeed solves the NULL pointer dereference, but floods a lot
>> with every page flip I have, e.g. !plane_state->visible == true
>> and crtc_state is not NULL and crtc_state->enable == true,
>> thus firing WARN_ON.
>> Is this something wrong with my use-case/driver or it is still legal
>> to have such a configuration and leave it without WARN_ON and just
>> return 0?
> 1 week of vacation later I have to admit that this WARN_ON is completely
> bogus :-)
np ;)
> Sorry for all the confusion, pls leave it out.
> -Daniel
>
>>>>>>> +
>>>>>>> +       if (plane_state->visible && crtc_state->enable)
>>>>>> Similar here.
>>>>>>
>>>>>>> + drm_mode_get_hv_timing(&crtc_state->mode,
>>>>>>> +                                      &clip.x2, &clip.y2);
>>>>>>> +
>>>>>>>            if (!plane_state->visible)
>>>>>>>                    return -EINVAL;
>>>>>> This can now be removed, the plane helper takes care of checking for
>>>>>> plane_state->visible != crtc_state->enable. Please also remove.
>>>>>>
>>>>>>>> We'd need to add a guarantee to
>>>>>>>> drm_atomic_helper_check_plane_state that
>>>>>>>> it can cope with crtc_state == NULL, but I think that's a good idea
>>>>>>>> anyway. Atm it shouldn't end up looking at the
>>>>>>>> crtc_state pointer in that
>>>>>>>> case.
>>>>>>> It doesn't look at it at the moment
>>>>>>>> Otherwise we'll just go with your fix, but it feels
>>>>>>>> all a bit too fragile,
>>>>>>>> hence why I want to explore more robust options a bit.
>>>>>>> At list with the change above it passes my test which failed
>>>>>>> before. Although I cannot confirm it works for others, but it
>>>>>>> certainly does for me.
>>>>>>>> -Daniel
>>>>>>> Do you want me to send v1 with the code above?
>>>>>> Yes please, with my above cleanup suggestions.
>>>>> Please see the patch under test attached (I believe it is what
>>>>> you mean,
>>>>> with the only change that
>>>>>       if (!plane_state->visible) {
>>>>>           *if (crtc_state)*
>>>>>               WARN_ON(crtc_state->enable);
>>>>>           return 0;
>>>>>       }
>>>>> check is used).
>>>>>
>>>>> Whith this patch + additional logs I have:
>>>>>
>>>>> [   18.939204] [drm:drm_ioctl [drm]] pid=2105, dev=0xe200, auth=1,
>>>>> DRM_IOCTL_MODE_ATOMIC
>>>>> [...]
>>>>> [   18.939681] [drm:drm_atomic_set_crtc_for_plane [drm]] Link
>>>>> plane state
>>>>> 00000000c302cbbf to [NOCRTC]
>>>>> [   18.939822] [drm:drm_atomic_set_fb_for_plane [drm]] Set
>>>>> [NOFB] for plane
>>>>> state 00000000c302cbbf
>>>>> [   18.939963] [drm:drm_atomic_print_state [drm]] checking
>>>>> 000000000bc224e7
>>>>> [   18.939988] vdispl vdispl.0: [drm] plane[29]: plane-0
>>>>> [   18.940003] vdispl vdispl.0: [drm]   crtc=(null)
>>>>> [   18.940018] vdispl vdispl.0: [drm]   fb=0
>>>>> [   18.940032] vdispl vdispl.0: [drm]   crtc-pos=0x0+0+0
>>>>> [   18.940048] vdispl vdispl.0: [drm]
>>>>> src-pos=0.000000x0.000000+0.000000+0.000000
>>>>> [   18.940067] vdispl vdispl.0: [drm]   rotation=1
>>>>> [   18.940199] [drm:drm_atomic_check_only [drm]] checking
>>>>> 000000000bc224e7
>>>>> [   18.940226] ================================= plane_state->visible 0
>>>>> crtc_state           (null)
>>>>> [...]
>>>>> [   18.978146] [drm:drm_atomic_set_crtc_for_plane [drm]] Link
>>>>> plane state
>>>>> 000000006bd50580 to [CRTC:30:crtc-0]
>>>>> [   18.978292] [drm:drm_atomic_set_fb_for_plane [drm]] Set
>>>>> [FB:35] for plane
>>>>> state 000000006bd50580
>>>>> [   18.978993] [drm:drm_atomic_set_mode_prop_for_crtc [drm]] Set
>>>>> [MODE:1024x768] for CRTC state 00000000e5a28f6a
>>>>> [   18.979425] [drm:drm_atomic_check_only [drm]] checking
>>>>> 000000000bc224e7
>>>>> [   18.979540] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>>>> [CRTC:30:crtc-0] mode changed
>>>>> [   18.979632] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>>>> [CRTC:30:crtc-0] enable changed
>>>>> [   18.979708] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>>>> [CRTC:30:crtc-0] active changed
>>>>> [   18.979792] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>>>> Updating routing for [CONNECTOR:28:Virtual-1]
>>>>> [   18.979877] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>>>> [CONNECTOR:28:Virtual-1] using [ENCODER:31:None-31] on [CRTC:30:crtc-0]
>>>>> [   18.979960] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]]
>>>>> [CRTC:30:crtc-0] needs all connectors, enable: y, active: y
>>>>> [   18.980139] [drm:drm_atomic_add_affected_connectors [drm]]
>>>>> Adding all
>>>>> current connectors for [CRTC:30:crtc-0] to 000000000bc224e7
>>>>> [   18.980184] ================================= plane_state->visible 0
>>>>> crtc_state 00000000e5a28f6a
>>>>> [   18.980205] crtc_state->enable 1
>>>>>
>>>>> *[   19.022608] WARNING: CPU: 1 PID: 2105 at
>>>>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>>>>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]*
>>>>>
>>>>> [...]
>>>>>
>>>>> [   19.113601] ================================= plane_state->visible 0
>>>>> crtc_state 00000000e5a28f6a
>>>>> [   19.113623] crtc_state->enable 1
>>>>> [   19.113792] WARNING: CPU: 1 PID: 2105 at
>>>>> drivers/gpu/drm/drm_simple_kms_helper.c:137
>>>>> drm_simple_kms_plane_atomic_check+0xdc/0xf8 [drm_kms_helper]
>>>>>
>>>>> [...]
>>>>>
>>>>> And finally
>>>>>
>>>>> [   19.340249] ================================= plane_state->visible 0
>>>>> crtc_state 0000000036a1b1f5
>>>>> [   19.340271] crtc_state->enable 0
>>>>>
>>>>> So, it seems that crtc_state can still be NULL if
>>>>> "!plane_state->visible"
>>>>> making
>>>>> NULL pointer dereference, so we need a check for that.
>>>>> Yet, !plane_state->visible && crtc_state->enable makes WARN_ON to fire
>>>>> always. So, probably we may want removing it.
>>>>>> Thanks, Daniel
>>>>> Thank you,
>>>>> Oleksandr
>>>>>   From dbcce708b237740158a2c16029c56a579324f269 Mon Sep 17 00:00:00 2001
>>>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>>>> Date: Tue, 13 Feb 2018 10:32:20 +0200
>>>>> Subject: [PATCH] drm/simple_kms_helper: Fix NULL pointer
>>>>> dereference with no
>>>>>    active CRTC
>>>>>
>>>>> It is possible that drm_simple_kms_plane_atomic_check called
>>>>> with no CRTC set, e.g. when user-space application sets CRTC_ID/FB_ID
>>>>> to 0 before doing any actual drawing. This leads to NULL pointer
>>>>> dereference because in this case new CRTC state is NULL and must be
>>>>> checked before accessing.
>>>>>
>>>>> Signed-off-by: Oleksandr Andrushchenko
>>>>> <oleksandr_andrushchenko@epam.com>
>>>>> ---
>>>>>    drivers/gpu/drm/drm_simple_kms_helper.c | 15 +++++++--------
>>>>>    1 file changed, 7 insertions(+), 8 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> index 9ca8a4a59b74..f54711ff9767 100644
>>>>> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
>>>>> @@ -121,12 +121,6 @@ static int
>>>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>>        pipe = container_of(plane, struct drm_simple_display_pipe,
>>>>> plane);
>>>>>        crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
>>>>>                               &pipe->crtc);
>>>>> -    if (!crtc_state->enable)
>>>>> -        return 0; /* nothing to check when disabling or disabled */
>>>>> -
>>>>> -    if (crtc_state->enable)
>>>>> -        drm_mode_get_hv_timing(&crtc_state->mode,
>>>>> -                       &clip.x2, &clip.y2);
>>>>>          ret = drm_atomic_helper_check_plane_state(plane_state,
>>>>> crtc_state,
>>>>>                              &clip,
>>>>> @@ -136,8 +130,13 @@ static int
>>>>> drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>>>        if (ret)
>>>>>            return ret;
>>>>>    -    if (!plane_state->visible)
>>>>> -        return -EINVAL;
>>>>> +    if (!plane_state->visible) {
>>>>> +        if (crtc_state)
>>>>> +            WARN_ON(crtc_state->enable);
>>>>> +        return 0;
>>>>> +    }
>>>>> +
>>>>> +    drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
>>>> lgtm. With or without the bikeshed to pull the crtc_state check into the
>>>> WARN_ON.
>>>>
>>>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>> Thank you
>>>> Please resubmit as a stand-alone patch, patchwork can't pull patches out
>>>> of attachments :-/
>>> oh, that was for demonstration purpose only, so we
>>> are on the same page and see the patch we are discussing ;)
>>>> -Daniel
>>>>
>>>>>          if (!pipe->funcs || !pipe->funcs->check)
>>>>>            return 0;
>>>>> -- 
>>>>> 2.7.4
>>>>>
>>>>> _______________________________________________
>>>>> dri-devel mailing list
>>>>> dri-devel@lists.freedesktop.org
>>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel