Starting with commit 17ce8a6907f7 ("drm/amd/display: Add dsc pre-validation in
atomic check"), amdgpu resets the CRTC state mode_changed flag to false when
recomputing the DSC configuration results in no timing change for a particular
stream.However, this is incorrect in scenarios where a change in MST/DSC configuration happens in the same KMS commit as another (unrelated) mode change. For example, the integrated panel of a laptop may be configured differently (e.g., HDR enabled/disabled) depending on whether external screens are attached. In this case, plugging in external DP-MST screens may result in the mode_changed flag being dropped incorrectly for the integrated panel if its DSC configuration did not change during precomputation in pre_validate_dsc(). At this point, however, dm_update_crtc_state() has already created new streams for CRTCs with DSC-independent mode changes. In turn, amdgpu_dm_commit_streams() will never release the old stream, resulting in a memory leak. amdgpu_dm_atomic_commit_tail() will never acquire a reference to the new stream either, which manifests as a use-after-free when the stream gets disabled later on: BUG: KASAN: use-after-free in dc_stream_release+0x25/0x90 [amdgpu] Write of size 4 at addr ffff88813d836524 by task kworker/9:9/29977 Workqueue: events drm_mode_rmfb_work_fn Call Trace: <TASK> dump_stack_lvl+0x6e/0xa0 print_address_description.constprop.0+0x88/0x320 ? dc_stream_release+0x25/0x90 [amdgpu] print_report+0xfc/0x1ff ? srso_alias_return_thunk+0x5/0xfbef5 ? __virt_addr_valid+0x225/0x4e0 ? dc_stream_release+0x25/0x90 [amdgpu] kasan_report+0xe1/0x180 ? dc_stream_release+0x25/0x90 [amdgpu] kasan_check_range+0x125/0x200 dc_stream_release+0x25/0x90 [amdgpu] dc_state_destruct+0x14d/0x5c0 [amdgpu] dc_state_release.part.0+0x4e/0x130 [amdgpu] dm_atomic_destroy_state+0x3f/0x70 [amdgpu] drm_atomic_state_default_clear+0x8ee/0xf30 ? drm_mode_object_put.part.0+0xb1/0x130 __drm_atomic_state_free+0x15c/0x2d0 atomic_remove_fb+0x67e/0x980 Since there is no reliable way of figuring out whether a CRTC has unrelated mode changes pending at the time of DSC validation, remember the value of the mode_changed flag from before the point where a CRTC was marked as potentially affected by a change in DSC configuration. Reset the mode_changed flag to this earlier value instead in pre_validate_dsc(). Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/5004 Fixes: 17ce8a6907f7 ("drm/amd/display: Add dsc pre-validation in atomic check") Signed-off-by: Yussuf Khalil <[email protected]> --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++ drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 1 + drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 4 +++- 3 files changed, 9 insertions(+), 1 deletion(-) 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 b3d6f2cd8..4efd77477 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -12523,6 +12523,11 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev, } if (dc_resource_is_dsc_encoding_supported(dc)) { + for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) { + dm_new_crtc_state = to_dm_crtc_state(new_crtc_state); + dm_new_crtc_state->mode_changed_independent_from_dsc = new_crtc_state->mode_changed; + } + for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) { if (drm_atomic_crtc_needs_modeset(new_crtc_state)) { ret = add_affected_mst_dsc_crtcs(state, crtc); diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h index 800813671..d15812d51 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h @@ -984,6 +984,7 @@ struct dm_crtc_state { bool freesync_vrr_info_changed; + bool mode_changed_independent_from_dsc; bool dsc_force_changed; bool vrr_supported; struct mod_freesync_config freesync_config; diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c index 7be50e8c0..5d8c4c702 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c @@ -1744,9 +1744,11 @@ int pre_validate_dsc(struct drm_atomic_state *state, int ind = find_crtc_index_in_state_by_stream(state, stream); if (ind >= 0) { + struct dm_crtc_state *dm_new_crtc_state = to_dm_crtc_state(state->crtcs[ind].new_state); + DRM_INFO_ONCE("%s:%d MST_DSC no mode changed for stream 0x%p\n", __func__, __LINE__, stream); - state->crtcs[ind].new_state->mode_changed = 0; + dm_new_crtc_state->base.mode_changed = dm_new_crtc_state->mode_changed_independent_from_dsc; } } } -- 2.53.0
