DF-4628

bxt_exec_gpio: function-static bxt_gpio_table caches devm-allocated gpio_descs across device unbind/rebind — use-after-free on gpiod_set_value

Summary

The static table caches descriptors owned by the drm device and freed by devres at unbind; never cleared on detach, so after a rebind the first panel-enable calls gpiod_set_value on stale freed descriptors - UAF write (flags/value), exploitable if the chunk is reclaimed. BXT + rebind cycle precondition; speculative per discipline. Per-device-table fix.

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: speculative
Pass: 2 · GLM 5.3 second pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
CWE: CWE-416
File: sys/dev/drm/i915/intel_dsi_vbt.c
Lines: 304-323
Area: dev
Discovered: 2026-09-22
Updated: 2026-09-22

Team triage

untriaged

priority: — · owner: —

PoC verification

untested

Status: untested
Reproduced: no
Impact: UAF write (gpiod_set_value mutates desc->flags/value) on first panel-enable after rebind; potentially exploitable if the freed chunk is reclaimed
Confidence: speculative
Tested: 2026-09-22 08:52:12
Attempts: 0
Runtime: —
Code hash: —
Guest: —
Build cmd: —
Run cmd: —

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Fix verification

not_testable

Fix status: not_testable
Baseline reproduced: no
Patched reproduced: no
Confidence: speculative
Tested: 2026-09-22 08:52:13
Runtime: —
Kernel: per-fix-DF-4628
fix.diff: findings/poc/DF-4628/fix.diff
Runner: df-bsd-reviewer

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PoC verification

Evidence pack

findings/poc/DF-4628 · 1 files

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

Fix verification

not_testable

baseline no→ patch + rebuild →patched clean

not_testable: hardware-gated (no Intel DSI panel / no mpt HBA on guest)

fix in finding markdown

per-fix-DF-4628

Confirmed kernel references

Detail

Exploit chain

[]

Evidence (decisive lines)

Function-static gpio table caches devm descriptors across device unbind/rebind with no invalidation. Per-device-table + clear-on-forget fix.

Verdict

not_run: BXT-class hardware + unbind/rebind cycle needed; speculative per pass-2 discipline