CVE-2025-40148

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Add NULL pointer checks in dc_stream cursor attribute functions

The function dc_stream_set_cursor_attributes() currently dereferences

the `stream` pointer and nested members `stream->ctx->dc->current_state`

without checking for NULL.

All callers of these functions, such as in

`dcn30_apply_idle_power_optimizations()` and

`amdgpu_dm_plane_handle_cursor_update()`, already perform NULL checks

before calling these functions.

Fixes below:

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:336 dc_stream_program_cursor_attributes()

error: we previously assumed 'stream' could be null (see line 334)

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c

327 bool dc_stream_program_cursor_attributes(

328 struct dc_stream_state *stream,

329 const struct dc_cursor_attributes *attributes)

330 {

331 struct dc *dc;

332 bool reset_idle_optimizations = false;

333

334 dc = stream ? stream->ctx->dc : NULL;

^^^^^^

The old code assumed stream could be NULL.

335

--> 336 if (dc_stream_set_cursor_attributes(stream, attributes)) {

^^^^^^

The refactor added an unchecked dereference.

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c

313 bool dc_stream_set_cursor_attributes(

314 struct dc_stream_state *stream,

315 const struct dc_cursor_attributes *attributes)

316 {

317 bool result = false;

318

319 if (dc_stream_check_cursor_attributes(stream, stream->ctx->dc->current_state, attributes)) {

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Here.

This function used to check for if stream as NULL and return false at

the start. Probably we should add that back.