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_andrushche...@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_andrushche...@epam.com>
Reviewed-by: Daniel Vetter <daniel.vet...@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
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