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CVE-2025-21985
drm/amd/display: Fix out-of-bound accesses
Published 2025-04-01 (19 months ago) by the Linux kernel CNA. Subsystem drivers/gpu. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2025-21985 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixed | 6.12.20-1 | Update the kernel and reboot. Fixed in 6.12.20-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.12.20-1 | Update the kernel and reboot. Fixed in 6.12.20-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.12.20-1 | Update the kernel and reboot. Fixed in 6.12.20-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
[WHAT & HOW] hpo_stream_to_link_encoder_mapping has size MAX_HPO_DP2_ENCODERS(=4), but location can have size up to 6. As a result, it is necessary to check location against MAX_HPO_DP2_ENCODERS. Similiarly, disp_cfg_stream_location can be used as an array index which should be 0..5, so the ASSERT's conditions should be less without equal.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_translation_helper.c
drivers/gpu/drm/amd/display/dc/dml2/dml2_translation_helper.c
- What this is
- AMD DISPLAY COREMAINTAINERS section matched on drivers/gpu/drm/amd/display/ · amd-gfx@lists.freedesktop.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2025-04-01 (19 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.20%, higher than 8.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/gpu
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.15 | 6.12.20 | 36793d90d76f |
| 4.15 | 6.13.8 | 9aedc776b110 |
| 4.15 | 6.14 | 8adbb2a98b00 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The vulnerable code is reached only through the local DRM atomic modeset ioctl (`DRM_IOCTL_MODE_ATOMIC`) on /dev/dri/card*, via amdgpu_dm_atomic_check() → dc_validate_global_state() → dml2_validate(); no network or remote peer data is involved.
- AC:LAttack complexity, low
- Once a DisplayPort configuration with five or more streams/planes exists (multi-monitor or MST/dock setups, SubVP phantom streams, or primaries plus an MPO overlay), the out-of-bounds index is hit deterministically on every validation pass, and the attacker can re-issue TEST_ONLY atomic commits repeatedly with plane/stream assignments of their choosing.
- PR:LPrivileges required, low
- The atomic ioctl is registered with DRM_MASTER only, which an ordinary unprivileged user holds for their active graphical session on the amdgpu card node — no root, no capability, and no init-namespace privilege is required.
- UI:NUser interaction, none
- The attacker performs the atomic commit themselves from their own session; no action by any other user is needed to trigger the out-of-bounds access.
- S:UScope, unchanged
- The corruption is confined to kernel heap memory belonging to the amdgpu display driver within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- The read at hpo_stream_to_link_encoder_mapping[4..5] pulls kernel data from beyond the array into adjacent struct state (g6_temp_read_watermark_set), and the resulting out-of-bounds heap write is a corruption primitive that can be leveraged to shape adjacent kernel objects for disclosure.
- I:HIntegrity impact, high
- The out-of-bounds value is used directly as an index into the 8-entry OutputEncoder[] array, producing a 4-byte write at a large, configuration-influenced offset that lands outside the kzalloc'd struct dml2_context, corrupting neighbouring heap objects as well as the DML output configuration that drives display hardware programming.
- A:HAvailability impact, high
- The wild write corrupts kernel heap memory and the display-config state used for bandwidth/watermark programming, leading to oops, slab corruption, or hung/underflowing display output requiring recovery.