CVE-2026-31488drm/amd/display: Do not skip unrelated mode changes in DSC validation

Official description

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Do not skip unrelated mode changes in DSC validation 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(). (cherry picked from commit cc7c7121ae082b7b82891baa7280f1ff2608f22b)

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/da1d0ed31e9802fd99384f43cc63678a5a11cb41
• https://git.kernel.org/stable/c/21159d8b335a6b9f44cbb506733013a902ae2da4
• https://git.kernel.org/stable/c/10862e344b4d6434642a48c87d765813fc0b0ba7
• https://git.kernel.org/stable/c/8a5edc97fd9c6415ff2eff872748439a97e3c3d8
• https://git.kernel.org/stable/c/111208b5b7ebcdadb3f922cc52d8425f0fa91b33
• https://git.kernel.org/stable/c/aed3d041ab061ec8a64f50a3edda0f4db7280025
• https://access.redhat.com/security/cve/CVE-2026-31488 vdb-entry, x_refsource_REDHAT
• RHBZ#2460619 issue-tracking, x_refsource_REDHAT
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31488.json x_sadp-csaf-vex
• https://access.redhat.com/errata/RHSA-2026:55445 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:53330 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:47739 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:43231 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:44385 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:30848 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:27353 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:47869 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:27354 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:47632 vendor-advisory, x_refsource_REDHAT
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html