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@xxxxxxxx>
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@xxxxxxxx>
---
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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