DF-5178

hw_hpd set_config consumes the gpio_config_data tagged union's hpd member without validating config_data->type

Summary

The only GPIO class that programs its union member blind (the DDC sibling discriminates) - a mismatched config would program garbage (masked MMIO) filter delays. No in-tree trigger (the sole caller always tags HPD); upstream shares the omission. Parity hardening; type-tag-check fix.

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Severity: Info
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: certain
Pass: 2 · GLM 5.3 second pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:N
CWE: CWE-843
File: sys/dev/drm/amd/display/dc/gpio/hw_hpd.c
Lines: 107-112
Area: dev
Discovered: 2026-09-30
Updated: 2026-09-30

Team triage

untriaged

priority: — · owner: —

PoC verification

untested

Status: untested
Reproduced: no
Impact: latent tagged-union confusion -> masked MMIO mis-programming
Confidence: certain
Tested: 2026-09-30 20:22:57
Attempts: 0
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 root@dfbsd:/usr/src/sys/X86_64_GENERIC x86_64
Build cmd: n/a
Run cmd: n/a

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Fix verification

not_testable

Fix status: not_testable
Baseline reproduced: no
Patched reproduced: no
Confidence: certain
Tested: 2026-09-30 20:22:57
Runtime: —
Kernel: per-fix-DF-5178
fix.diff: findings/poc/DF-5178/fix.diff
Runner: df-bsd-reviewer

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PoC verification

Evidence pack

findings/poc/DF-5178 · 1 files

File	Type	Description	Size
verdict.json	file		1.0 KB	view raw

Fix verification

not_testable

baseline no→ patch + rebuild →patched clean

per-fix-DF-5178

Confirmed kernel references

Detail

Evidence (decisive lines)

source trace: hw_hpd.c:107-112 vs the discriminating hw_ddc.c:99-127

Verified recommended fix

reject config_data->type != GPIO_CONFIG_TYPE_HPD

Verdict

untested (no in-tree trigger; Info parity hardening on AMD-only paths)