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Subject[PATCH] drm/simple_kms_helper: Fix NULL pointer dereference with no active CRTC
Date
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;

if (crtc_state->enable)
drm_mode_get_hv_timing(&crtc_state->mode,
--
2.7.4
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