DF-1623

NULL-pointer dereference in atmel_reset_device when cmdprocobj (T6) object is absent

Summary

atmel_mxt.c:418 sc->cmdprocobj = mxt_findobject(T6) NO NULL check (only msgprocobj T5 checked at 417-423). 437 init_device success -> atmel_reset_device -> 983 mxt_write_object_off(sc, sc->cmdprocobj, ...) derefs obj->start_pos_lsb -> NULL page fault panic. Poll thread reset path at 941 same unchecked call. Attacker: malicious I2C peripheral at 0x4A reporting T5 but omitting T6 -> kernel panic at attach. Fix: require cmdprocobj!=NULL in init_device + NULL guard in atmel_reset_device.

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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 NULL Pointer Dereference
File: sys/dev/smbus/atmel_mxt/atmel_mxt.c
Lines: 418-983
Area: dev
Discovered: 2026-07-18
Updated: 2026-07-18

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: likely
Tested: 2026-07-23 17:00:08
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 17:00:08
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1623/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1623 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	551 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-1623 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: atmel_mxt.c:418 sc->cmdprocobj = mxt_findobject(T6) NO NULL check (only msgprocobj T5 checked at 417-423). 437 init_device success -> atmel_reset_device -> 983 mxt_write_object_off(sc, sc->cmdprocobj,

Citation: sys/dev/smbus/atmel_mxt/atmel_mxt.c:418-983

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: cmdprocobj NULL deref when T6 object missing (atmel_mxt.c:418-425,983)

Verified recommended fix

Source-confirmed: cmdprocobj NULL deref when T6 object missing (atmel_mxt.c:418-425,983)

Verdict

Source-confirmed: cmdprocobj NULL deref when T6 object missing (atmel_mxt.c:418-425,983)