[PATCH] drm/amd/display: avoid null pointer dereference in dm_set_vblank

[Defang Bo]

[Why]
Similar to commit<dddc0557e>("drm/amd/display: Guard against null crtc in CRC 
IRQ"),
a null pointer deference can occur if crtc is null in
dm_set_vblank.

[How]

Check that CRTC is non-null before accessing its fields.

Signed-off-by: Defang Bo <bodef...@126.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index e2b23486..df23d28 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4875,10 +4875,17 @@ static inline int dm_set_vupdate_irq(struct drm_crtc 
*crtc, bool enable)
 static inline int dm_set_vblank(struct drm_crtc *crtc, bool enable)
 {
        enum dc_irq_source irq_source;
-       struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
-       struct amdgpu_device *adev = drm_to_adev(crtc->dev);
-       struct dm_crtc_state *acrtc_state = to_dm_crtc_state(crtc->state);
+       struct amdgpu_crtc *acrtc;
+       struct amdgpu_device *adev;
+       struct dm_crtc_state *acrtc_state;
        int rc = 0;
+
+       if (crtc == NULL)
+               return rc;
+
+       acrtc = to_amdgpu_crtc(crtc);
+       adev = drm_to_adev(crtc->dev);
+       acrtc_state = to_dm_crtc_state(crtc->state);
 
        if (enable) {
                /* vblank irq on -> Only need vupdate irq in vrr mode */
-- 
2.7.4