DF-1111

Ignored copyin/copyout return values in I2CRDWR leak uninitialized kernel heap to I2C bus

Summary

I2CRDWR message loop: m->buf=kmalloc(m->len,M_TEMP,M_WAITOK) at :360 WITHOUT M_ZERO. copyin of write data at :362 ignores return value; on failure m->buf retains stale/uninitialized kernel heap memory which is then transmitted to I2C device via iicbus_transfer at :364. copyout at :369 likewise ignores return value. Root attacker with controlled I2C peripheral can pass write message with invalid buf pointer -> copyin fails silently -> uninitialized heap bytes clocked out to slave. Fix: allocate M_ZERO and check copyin return, zeroing len on failure.

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Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U:C:L/I:N/A:N
CWE: CWE-252 Unchecked Return Value; CWE-908 Use of Uninitialized Resource
File: sys/bus/iicbus/iic.c
Lines: 360-369
Area: hw
Discovered: 2026-07-15
Updated: 2026-07-15

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: leak
Confidence: certain
Tested: 2026-07-25 10:25:03
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: 2026-07-25 10:25:03
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1111/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1111 · 3 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-1111	622 B	↓ raw
fix.diff	suggested-fix	Use M_ZERO and check copyin return for I2C write data	962 B	view raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-1111

↓ download raw

DF-1111 Verification Verdict

Severity: Low Impact class: leak Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: Use M_ZERO and check copyin return for I2C write data

Fix applied and validated in batch kernel build (rc=0, -Werror).

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): I2CRDWR loop: m->buf=kmalloc(m->len,M_TEMP,M_WAITOK) WITHOUT M_ZERO; copyin of write data ignores return value; on failure m->buf retains stale kernel heap memory which is th

Verified recommended fix

REPRODUCED (source-only): I2CRDWR loop: m->buf=kmalloc(m->len,M_TEMP,M_WAITOK) WITHOUT M_ZERO; copyin of write data ignores return value; on failure m->buf retains stale kernel heap memory which is then transferred.