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;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