amdgpu_dm_crtc_set_vblank() dereferences acrtc_state->stream when
vblank is enabled/queried from DRM_IOCTL_MODE_CRTC_GET_SEQUENCE before
a stream is attached to it.

BUG: kernel NULL pointer dereference, address: 0000000000000008
RIP: amdgpu_dm_crtc_set_vblank+0x6b/0x4d0 [amdgpu]
Call Trace:
 drm_vblank_enable
 drm_vblank_get
 drm_crtc_get_sequence_ioctl
 drm_ioctl_kernel
 drm_ioctl

Reproduced by running VKCTS with WSI tests enabled on RADV.

Guard the enable path on acrtc_state->stream being non-NULL, matching
the existing checks in this function.

Fixes: 34d66bc7ff10 ("drm/amd/display: Fix Xorg desktop unresponsive on Replay 
panel")
Signed-off-by: Samuel Pitoiset <[email protected]>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
index 46d85457c77b..62eac6e65334 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
@@ -268,7 +268,7 @@ static inline int amdgpu_dm_crtc_set_vblank(struct drm_crtc 
*crtc, bool enable)
 
        irq_type = amdgpu_display_crtc_idx_to_irq_type(adev, acrtc->crtc_id);
 
-       if (enable) {
+       if (enable && acrtc_state->stream) {
                struct dc *dc = adev->dm.dc;
                struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc);
                struct psr_settings *psr = 
&acrtc_state->stream->link->psr_settings;
-- 
2.54.0

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