DF-1934

NULL-deref panic in dce4_hdmi_set_color_depth when radeon_get_connector_for_encoder returns NULL

Summary

dce4_hdmi_set_color_depth L342 connector=radeon_get_connector_for_encoder(encoder) no NULL check before connector->name in DRM_DEBUG L355/361/367. radeon_get_connector_for_encoder returns NULL when active_device matches no connector on unlocked connector_list. Sibling evergreen_hdmi_enable L437 and evergreen_dp_enable L476 explicitly test connector&&. DRM_DEBUG evaluates args unconditionally before drm_dbg early-return so crash not gated on drm_debug. Caller radeon_hdmi_set_color_depth radeon_audio.c:657 only checks dig&&dig->afmt not connector. Reachable: race display hot-unplug/MST reconfig against mode_set. NULL deref on connector->name load offset ~40. Local DoS panic. Fix: conn_name = connector?connector->name:none.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: likely
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/radeon/evergreen_hdmi.c
Lines: 342-367
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: likely
Tested: 2026-07-23 17:00:16
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: likely
Tested: 2026-07-23 17:00:16
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1934/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1934 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	439 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-1934 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: dce4_hdmi_set_color_depth L342 connector=radeon_get_connector_for_encoder(encoder) no NULL check before connector->name in DRM_DEBUG L355/361/367. radeon_get_connector_for_encoder returns NULL when ac

Citation: sys/dev/drm/radeon/evergreen_hdmi.c:342-367

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: connector->name NULL deref in DRM_DEBUG (evergreen_hdmi.c:342-367)

Verified recommended fix

Source-confirmed: connector->name NULL deref in DRM_DEBUG (evergreen_hdmi.c:342-367)

Verdict

Source-confirmed: connector->name NULL deref in DRM_DEBUG (evergreen_hdmi.c:342-367)