[PATCH v1] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[PATCH v1] 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>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

---
Changes since initial:
- re-worked checks for null CRTC as suggested by Daniel Vetter
---
 drivers/gpu/drm/drm_simple_kms_helper.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 9ca8a4a59b74..4a1dbd88b1ec 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,
@@ -137,7 +131,9 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
 		return ret;
 
 	if (!plane_state->visible)
-		return -EINVAL;
+		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 v1] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/22/2018 08:09 AM, 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>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> ---
> Changes since initial:
> - re-worked checks for null CRTC as suggested by Daniel Vetter
> ---
>   drivers/gpu/drm/drm_simple_kms_helper.c | 10 +++-------
>   1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 9ca8a4a59b74..4a1dbd88b1ec 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,
> @@ -137,7 +131,9 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>   		return ret;
>   
>   	if (!plane_state->visible)
> -		return -EINVAL;
Daniel, I have put your R-b tag, but I had removed suggested
"WARN_ON(crtc_state && crtc_state->enable);"
here as it fires each time when crtc_state is not NULL.
Please let me know if this is not ok and you want me to remove
your R-b tag.
> +		return 0;
> +
> +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
>   
>   	if (!pipe->funcs || !pipe->funcs->check)
>   		return 0;
Thank you,
Oleksandr

Re: [PATCH v1] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Daniel Vetter]

On Thu, Feb 22, 2018 at 08:12:48AM +0200, Oleksandr Andrushchenko wrote:
> On 02/22/2018 08:09 AM, 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>
> > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > 
> > ---
> > Changes since initial:
> > - re-worked checks for null CRTC as suggested by Daniel Vetter
> > ---
> >   drivers/gpu/drm/drm_simple_kms_helper.c | 10 +++-------
> >   1 file changed, 3 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> > index 9ca8a4a59b74..4a1dbd88b1ec 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,
> > @@ -137,7 +131,9 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> >   		return ret;
> >   	if (!plane_state->visible)
> > -		return -EINVAL;
> Daniel, I have put your R-b tag, but I had removed suggested
> "WARN_ON(crtc_state && crtc_state->enable);"
> here as it fires each time when crtc_state is not NULL.
> Please let me know if this is not ok and you want me to remove
> your R-b tag.

I'm a bit confused why that fires, but oh well. Applied, thanks for your
patch.
-Daniel

> > +		return 0;
> > +
> > +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
> >   	if (!pipe->funcs || !pipe->funcs->check)
> >   		return 0;
> Thank you,
> Oleksandr
> _______________________________________________
> 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 v1] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC

[Oleksandr Andrushchenko]

On 02/22/2018 06:11 PM, Daniel Vetter wrote:
> On Thu, Feb 22, 2018 at 08:12:48AM +0200, Oleksandr Andrushchenko wrote:
>> On 02/22/2018 08:09 AM, 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>
>>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>>
>>> ---
>>> Changes since initial:
>>> - re-worked checks for null CRTC as suggested by Daniel Vetter
>>> ---
>>>    drivers/gpu/drm/drm_simple_kms_helper.c | 10 +++-------
>>>    1 file changed, 3 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
>>> index 9ca8a4a59b74..4a1dbd88b1ec 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,
>>> @@ -137,7 +131,9 @@ static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
>>>    		return ret;
>>>    	if (!plane_state->visible)
>>> -		return -EINVAL;
>> Daniel, I have put your R-b tag, but I had removed suggested
>> "WARN_ON(crtc_state && crtc_state->enable);"
>> here as it fires each time when crtc_state is not NULL.
>> Please let me know if this is not ok and you want me to remove
>> your R-b tag.
> I'm a bit confused why that fires, but oh well. Applied, thanks for your
> patch.
Thank you
> -Daniel
>
>>> +		return 0;
>>> +
>>> +	drm_mode_get_hv_timing(&crtc_state->mode, &clip.x2, &clip.y2);
>>>    	if (!pipe->funcs || !pipe->funcs->check)
>>>    		return 0;
>> Thank you,
>> Oleksandr
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel