[PATCH] drm/amd/display: Fix NULL pointer dereferences in dm_update_crtc_state()

[Srinivasan Shanmugam]

Added checks for NULL values after retrieving drm_new_conn_state and
drm_old_conn_state to prevent dereferencing NULL pointers.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:10751 dm_update_crtc_state()
	warn: 'drm_new_conn_state' can also be NULL

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c
    10672 static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
    10673                          struct drm_atomic_state *state,
    10674                          struct drm_crtc *crtc,
    10675                          struct drm_crtc_state *old_crtc_state,
    10676                          struct drm_crtc_state *new_crtc_state,
    10677                          bool enable,
    10678                          bool *lock_and_validation_needed)
    10679 {
    10680         struct dm_atomic_state *dm_state = NULL;
    10681         struct dm_crtc_state *dm_old_crtc_state, *dm_new_crtc_state;
    10682         struct dc_stream_state *new_stream;
    10683         int ret = 0;
    10684
    ...
    10703
    10704         /* TODO This hack should go away */
    10705         if (connector && enable) {
    10706                 /* Make sure fake sink is created in plug-in scenario */
    10707                 drm_new_conn_state = drm_atomic_get_new_connector_state(state,
    10708                                                                         connector);

drm_atomic_get_new_connector_state() can't return error pointers, only NULL.

    10709                 drm_old_conn_state = drm_atomic_get_old_connector_state(state,
    10710                                                                         connector);
    10711
    10712                 if (IS_ERR(drm_new_conn_state)) {
                                     ^^^^^^^^^^^^^^^^^^

    10713                         ret = PTR_ERR_OR_ZERO(drm_new_conn_state);

Calling PTR_ERR_OR_ZERO() doesn't make sense.  It can't be success.

    10714                         goto fail;
    10715                 }
    10716
    ...
    10748
    10749                 dm_new_crtc_state->abm_level = dm_new_conn_state->abm_level;
    10750
--> 10751                 ret = fill_hdr_info_packet(drm_new_conn_state,
                                                     ^^^^^^^^^^^^^^^^^^ Unchecked dereference

    10752                                            &new_stream->hdr_static_metadata);
    10753                 if (ret)
    10754                         goto fail;
    10755

Cc: Harry Wentland <harry.wentland at amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
Cc: Tom Chung <chiahsuan.chung at amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Cc: Roman Li <roman.li at amd.com>
Cc: Alex Hung <alex.hung at amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
Reported-by: Dan Carpenter <dan.carpenter at linaro.org>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 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 1b92930119cc..e3df11662fff 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -10727,11 +10727,20 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
 		drm_old_conn_state = drm_atomic_get_old_connector_state(state,
 									connector);
 
-		if (IS_ERR(drm_new_conn_state)) {
-			ret = PTR_ERR_OR_ZERO(drm_new_conn_state);
-			goto fail;
+		/* Check if drm_new_conn_state is valid */
+		if (drm_new_conn_state) {
+			dm_new_conn_state = to_dm_connector_state(drm_new_conn_state);
+
+			/* Attempt to fill HDR info packet */
+			ret = fill_hdr_info_packet(drm_new_conn_state,
+						   &new_stream->hdr_static_metadata);
+			if (ret)
+				goto fail;
 		}
 
+		if (drm_old_conn_state)
+			dm_old_conn_state = to_dm_connector_state(drm_old_conn_state);
+
 		dm_new_conn_state = to_dm_connector_state(drm_new_conn_state);
 		dm_old_conn_state = to_dm_connector_state(drm_old_conn_state);
 
@@ -10766,11 +10775,6 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
 
 		dm_new_crtc_state->abm_level = dm_new_conn_state->abm_level;
 
-		ret = fill_hdr_info_packet(drm_new_conn_state,
-					   &new_stream->hdr_static_metadata);
-		if (ret)
-			goto fail;
-
 		/*
 		 * If we already removed the old stream from the context
 		 * (and set the new stream to NULL) then we can't reuse
-- 
2.34.1