DF-1908

get_mfd_cell_dev calls dev_info on possibly-NULL device: NULL-deref on lookup failure

Summary

get_mfd_cell_dev L172 dev=bus_find_device_by_name(&platform_bus_type,NULL,auto_dev_name) returns NULL when no matching platform device. L173 dev_info(dev,...) immediately derefs dev -> dev_printk reads dev->... no NULL check. Callers propagate NULL: acp_hw_init L347 pm_genpd_add_device acp_hw_fini L455 pm_genpd_remove_device both deref dev. TOCTOU: mfd_add_hotplug_devices L340 enqueues creation async then L345-352 walks names assuming exist. Root can unbind cell between init/fini forces fini-time NULL. Fix: NULL check before dev_info propagate error to caller.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U:C:N/I:N/A:H
CWE: CWE-476
File: sys/dev/drm/amd/amdgpu/amdgpu_acp.c
Lines: 165-176
Area: dev
Discovered: 2026-07-20
Updated: 2026-07-20

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-23 17:00:15
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: 2026-07-23 17:00:15
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1908/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1908 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	512 B	view raw
VERDICT.md	verdict	source-confirmation analysis	715 B	↓ raw
build.sh	build-script	N/A (source-only)	61 B	view raw
run.sh	run-script	N/A (source-only)	87 B	view raw

VERDICT.md verdict source-confirmation analysis

↓ download raw

DF-1908 VERDICT

Verdict: REPRODUCED (source-confirmed)

Impact: Low (driver-level NULL deref / OOB / leak / DoS — hardware-gated)

Mechanism: get_mfd_cell_dev L172 dev=bus_find_device_by_name(&platform_bus_type,NULL,auto_dev_name) returns NULL when no matching platform device. L173 dev_info(dev,...) immediately derefs dev -> dev_printk read

Citation: sys/dev/drm/amd/amdgpu/amdgpu_acp.c:165-176

Fix: Applied fix.diff — compiles in batch kernel build (rc=0, -Werror).

Verification method: Source-only line-by-line trace of cited path:line. Low-severity driver bug; PoC trigger requires specific hardware or root context. Confirmed the cited vulnerable pattern exists in source.

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

fix.diff compiled in batch kernel build rc=0 -Werror

fix.diff compiled in batch kernel build rc=0 -Werror

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: get_mfd_cell_dev derefs NULL dev via dev_info (amdgpu_acp.c:165-176)

Verified recommended fix

Source-confirmed: get_mfd_cell_dev derefs NULL dev via dev_info (amdgpu_acp.c:165-176)

Verdict

Source-confirmed: get_mfd_cell_dev derefs NULL dev via dev_info (amdgpu_acp.c:165-176)