[PATCH 12/41] drm/amd/display: Fix wb_info leak and NULL deref in writeback

[<Roman.Li@amd.com>]

From: Alex Hung <alex.hung@amd.com>

[WHAT]
dc_stream_add_writeback() copies wb_info by value, so free it on all
paths via a single cleanup label. Also bail out early when no pipe_ctx
matches the stream to avoid a NULL pointer dereference.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c    | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 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 0dcf829c1d07..52c1ffad985b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4647,21 +4647,19 @@ static void dm_set_writeback(struct amdgpu_display_manager *dm,
 	wb_info = kzalloc_obj(*wb_info);
 	if (!wb_info) {
 		drm_err(adev_to_drm(adev), "Failed to allocate wb_info\n");
-		return;
+		goto cleanup;
 	}
 
 	acrtc = to_amdgpu_crtc(wb_conn->encoder.crtc);
 	if (!acrtc) {
 		drm_err(adev_to_drm(adev), "no amdgpu_crtc found\n");
-		kfree(wb_info);
-		return;
+		goto cleanup;
 	}
 
 	afb = to_amdgpu_framebuffer(new_con_state->writeback_job->fb);
 	if (!afb) {
 		drm_err(adev_to_drm(adev), "No amdgpu_framebuffer found\n");
-		kfree(wb_info);
-		return;
+		goto cleanup;
 	}
 
 	for (i = 0; i < MAX_PIPES; i++) {
@@ -4671,6 +4669,11 @@ static void dm_set_writeback(struct amdgpu_display_manager *dm,
 		}
 	}
 
+	if (!pipe) {
+		drm_err(adev_to_drm(adev), "No pipe found for stream\n");
+		goto cleanup;
+	}
+
 	/* fill in wb_info */
 	wb_info->wb_enabled = true;
 
@@ -4744,6 +4747,9 @@ static void dm_set_writeback(struct amdgpu_display_manager *dm,
 	WARN_ON(drm_crtc_vblank_get(&acrtc->base));
 	acrtc->wb_frame_done = false;
 	acrtc->wb_pending = true;
+
+cleanup:
+	kfree(wb_info);
 }
 
 static void amdgpu_dm_update_hdcp(struct drm_atomic_commit *state)
-- 
2.34.1