[PATCH 7.1 110/228] drm/amd/display: Fix NULL pointer dereference in amdgpu_dm_crtc_set_vblank()

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Samuel Pitoiset <[email protected]>

commit f2a1c4c6fe0a6fcde02e59dde546dba28d283635 upstream.

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")
Reviewed-by: Melissa Wen <[email protected]>
Signed-off-by: Samuel Pitoiset <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
(cherry picked from commit 7b1b31bf6942e6f43509b48da23f8e27269aac39)
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
@@ -287,7 +287,7 @@ static inline int amdgpu_dm_crtc_set_vbl
 
 	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;