DF-1154

Unbounded per-CRTC plane count can overflow MAX_SURFACES stack/heap buffers

Summary

commit_planes_to_stream (:4496 plane_states_constructed[MAX_SURFACES=3]) and dm_determine_update_type_for_commit (:5535 updates/surface[MAX_SURFACES]) use fixed arrays but planes_count/num_plane has no bounds check. Currently masked by hardware: per-CRTC plane count structurally <=2 on all in-tree ASICs. If future DCN exposes >=3 overlay planes per CRTC: stack smash in commit path with attacker-influenced pointer data -> RIP control. Fix: add planes_count<MAX_SURFACES guard.

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: speculative
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U:C:H/I:H/A:H
CWE: CWE-787 Out-of-bounds Write
File: sys/dev/drm/amd/display/amdgpu_dm/amdgpu_dm.c
Lines: 4496-5593
Area: dev
Discovered: 2026-07-15
Updated: 2026-07-15

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-25 10:25:04
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-25 10:25:04
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1154/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1154 · 3 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-1154	635 B	↓ raw
fix.diff	suggested-fix	Add planes_count<MAX_SURFACES bounds guard before array index	478 B	view raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-1154

↓ download raw

DF-1154 Verification Verdict

Severity: Low Impact class: oob_write Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: Add planes_count<MAX_SURFACES bounds guard before array index

Fix applied and validated in batch kernel build (rc=0, -Werror).

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): commit_planes_to_stream and dm_determine_update_type_for_commit use fixed arrays plane_states_constructed[MAX_SURFACES=3]/updates[MAX_SURFACES] but planes_count has no bounds

Verified recommended fix

REPRODUCED (source-only): commit_planes_to_stream and dm_determine_update_type_for_commit use fixed arrays plane_states_constructed[MAX_SURFACES=3]/updates[MAX_SURFACES] but planes_count has no bounds check. OOB write.