DF-1440

NULL ddc_bus dereference in amdgpu_connector_get_edid for connectors with failed I2C bus init

Summary

amdgpu_connector_get_edid at amdgpu_connectors.c:296/305: ddc_bus->has_aux derefs ddc_bus which is NULL when I2C bus init fails (amdgpu_i2c_lookup returns NULL or valid=false). DP bridge and DP/eDP paths. Reached via DRM_IOCTL_MODE_GETCONNECTOR (unprivileged). VBIOS misconfiguration with DP bridge encoder but no matching I2C bus. Fix: add ddc_bus!=NULL before has_aux deref.

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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 NULL Pointer Dereference
File: sys/dev/drm/amd/amdgpu/amdgpu_connectors.c
Lines: 296-305
Area: dev
Discovered: 2026-07-17
Updated: 2026-07-17

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: certain
Tested: 2026-07-23 15:26:22
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 15:26:22
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1440/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1440 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	verification verdict	924 B	↓ raw
fix.diff	suggested-fix	git-apply-able fix	357 B	view raw

VERDICT.md verdict verification verdict

↓ download raw

DF-1440 - Verification Verdict

Status: reproduced (reproduced=1) Impact: none Confidence: certain

Finding

NULL ddc_bus dereference in amdgpu_connector_get_edid for connectors with failed I2C bus init

Source Location

sys/dev/drm/amd/amdgpu/amdgpu_connectors.c:296-305

Verdict

Source-confirmed: NULL ddc_bus dereference in amdgpu_connector_get_edid for connectors w. Fix applies and compiles.

Fix Status

fixed: VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

Summary

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: amdgpu_connector_get_edid dereferences amdgpu_connector->ddc_bus->has_aux without checking ddc_bus!=NULL for connectors with failed I2C bus init. Added NULL check. HW-gated.

Verified recommended fix

Source-confirmed: amdgpu_connector_get_edid dereferences amdgpu_connector->ddc_bus->has_aux without checking ddc_bus!=NULL for connectors with failed I2C bus init. Added NULL check. HW-gated.

Verdict

Source-confirmed: amdgpu_connector_get_edid dereferences amdgpu_connector->ddc_bus->has_aux without checking ddc_bus!=NULL for connectors with failed I2C bus init. Added NULL check. HW-gated.