[PATCH 41/43] drm/amd/display: fix a bug to dereference already freed old current state memory

[Wayne Lin]

From: Wenjing Liu <wenjing.liu at amd.com>

[why]
During minimal transition commit, the base state could be freed if it is current state.
This is because after committing minimal transition state, the current state will be
swapped to the minimal transition state and the old current state will be released.
the release could cause the old current state's memory to be freed. However dc
will derefernce this memory when release minimal transition state. Therefore, we
need to retain the old current state until we release minimal transition state.

Cc: Mario Limonciello <mario.limonciello at amd.com>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: stable at vger.kernel.org
Reviewed-by: Josip Pavic <josip.pavic at amd.com>
Acked-by: Wayne Lin <wayne.lin at amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index a372c4965adf..ab0c920333be 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -4203,7 +4203,6 @@ static void release_minimal_transition_state(struct dc *dc,
 {
 	restore_minimal_pipe_split_policy(dc, base_context, policy);
 	dc_state_release(minimal_transition_context);
-	/* restore previous pipe split and odm policy */
 }
 
 static void force_vsync_flip_in_minimal_transition_context(struct dc_state *context)
@@ -4258,7 +4257,7 @@ static bool is_pipe_topology_transition_seamless_with_intermediate_step(
 					intermediate_state, final_state);
 }
 
-static void swap_and_free_current_context(struct dc *dc,
+static void swap_and_release_current_context(struct dc *dc,
 		struct dc_state *new_context, struct dc_stream_state *stream)
 {
 
@@ -4321,7 +4320,7 @@ static bool commit_minimal_transition_based_on_new_context(struct dc *dc,
 			commit_planes_for_stream(dc, srf_updates,
 					surface_count, stream, NULL,
 					UPDATE_TYPE_FULL, intermediate_context);
-			swap_and_free_current_context(
+			swap_and_release_current_context(
 					dc, intermediate_context, stream);
 			dc_state_retain(dc->current_state);
 			success = true;
@@ -4338,6 +4337,7 @@ static bool commit_minimal_transition_based_on_current_context(struct dc *dc,
 	bool success = false;
 	struct pipe_split_policy_backup policy;
 	struct dc_state *intermediate_context;
+	struct dc_state *old_current_state = dc->current_state;
 	struct dc_surface_update srf_updates[MAX_SURFACE_NUM];
 	int surface_count;
 
@@ -4353,8 +4353,10 @@ static bool commit_minimal_transition_based_on_current_context(struct dc *dc,
 	 * with the current state.
 	 */
 	restore_planes_and_stream_state(&dc->scratch.current_state, stream);
+	dc_state_retain(old_current_state);
 	intermediate_context = create_minimal_transition_state(dc,
-			dc->current_state, &policy);
+			old_current_state, &policy);
+
 	if (intermediate_context) {
 		if (is_pipe_topology_transition_seamless_with_intermediate_step(
 				dc,
@@ -4367,14 +4369,15 @@ static bool commit_minimal_transition_based_on_current_context(struct dc *dc,
 			commit_planes_for_stream(dc, srf_updates,
 					surface_count, stream, NULL,
 					UPDATE_TYPE_FULL, intermediate_context);
-			swap_and_free_current_context(
+			swap_and_release_current_context(
 					dc, intermediate_context, stream);
 			dc_state_retain(dc->current_state);
 			success = true;
 		}
 		release_minimal_transition_state(dc, intermediate_context,
-				dc->current_state, &policy);
+				old_current_state, &policy);
 	}
+	dc_state_release(old_current_state);
 	/*
 	 * Restore stream and plane states back to the values associated with
 	 * new context.
@@ -4496,12 +4499,14 @@ static bool commit_minimal_transition_state(struct dc *dc,
 			dc->debug.pipe_split_policy != MPC_SPLIT_AVOID ? "MPC in Use" :
 			"Unknown");
 
+	dc_state_retain(transition_base_context);
 	transition_context = create_minimal_transition_state(dc,
 			transition_base_context, &policy);
 	if (transition_context) {
 		ret = dc_commit_state_no_check(dc, transition_context);
 		release_minimal_transition_state(dc, transition_context, transition_base_context, &policy);
 	}
+	dc_state_release(transition_base_context);
 
 	if (ret != DC_OK) {
 		/* this should never happen */
@@ -4839,7 +4844,7 @@ static bool update_planes_and_stream_v2(struct dc *dc,
 				context);
 	}
 	if (dc->current_state != context)
-		swap_and_free_current_context(dc, context, stream);
+		swap_and_release_current_context(dc, context, stream);
 	return true;
 }
 
@@ -4941,7 +4946,7 @@ static bool update_planes_and_stream_v3(struct dc *dc,
 		commit_planes_and_stream_update_with_new_context(dc,
 				srf_updates, surface_count, stream,
 				stream_update, update_type, new_context);
-		swap_and_free_current_context(dc, new_context, stream);
+		swap_and_release_current_context(dc, new_context, stream);
 	}
 
 	return true;
-- 
2.37.3