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 

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 
Reviewed-by: Daniel Vetter 

---
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,
   >crtc);
-   if (!crtc_state->enable)
-   return 0; /* nothing to check when disabling or disabled */
-
-   if (crtc_state->enable)
-   drm_mode_get_hv_timing(_state->mode,
-  , );
ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
  ,
@@ -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(_state->mode, , );
if (!pipe->funcs || !pipe->funcs->check)
return 0;

Thank you,
Oleksandr
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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 
> > 
> > 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 
> > Reviewed-by: Daniel Vetter 
> > 
> > ---
> > 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,
> >>crtc);
> > -   if (!crtc_state->enable)
> > -   return 0; /* nothing to check when disabling or disabled */
> > -
> > -   if (crtc_state->enable)
> > -   drm_mode_get_hv_timing(_state->mode,
> > -  , );
> > ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
> >   ,
> > @@ -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(_state->mode, , );
> > if (!pipe->funcs || !pipe->funcs->check)
> > return 0;
> Thank you,
> Oleksandr
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> dri-devel@lists.freedesktop.org
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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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 

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 
Reviewed-by: Daniel Vetter 

---
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,
   >crtc);
-   if (!crtc_state->enable)
-   return 0; /* nothing to check when disabling or disabled */
-
-   if (crtc_state->enable)
-   drm_mode_get_hv_timing(_state->mode,
-  , );
  
  	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,

  ,
@@ -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(_state->mode, , );
  
  	if (!pipe->funcs || !pipe->funcs->check)

return 0;

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

[Oleksandr Andrushchenko]

From: Oleksandr Andrushchenko 

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 
Reviewed-by: Daniel Vetter 

---
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,
   >crtc);
-   if (!crtc_state->enable)
-   return 0; /* nothing to check when disabling or disabled */
-
-   if (crtc_state->enable)
-   drm_mode_get_hv_timing(_state->mode,
-  , );
 
ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
  ,
@@ -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(_state->mode, , );
 
if (!pipe->funcs || !pipe->funcs->check)
return 0;
-- 
2.7.4

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