DF-1348

Unbounded bcopy of CDB into CmdBlock[12] overflows SRB on >12-byte CDBs

Summary

amd_action XPT_SCSI_IO at amd.c:399-400: bcopy(cdb_bytes,CmdBlock,cdb_len). CmdBlock[12] (amd.h:159). cdb_len u8 from CAM. cdb_len>12 overflows into pccb pointer. 16-byte CDB lands in padding on amd64. cdb_len>=17 corrupts pccb -> deref at :240. Sibling of DF-1235/DF-1270. Root/operator via pass(4). Fix: check cdb_len<=sizeof(CmdBlock).

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U:C:N/I:L/A:L
CWE: CWE-120 Buffer Copy without Checking Size of Input
File: sys/dev/disk/amd/amd.c
Lines: 399-400
Area: dev
Discovered: 2026-07-16
Updated: 2026-07-16

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: likely
Tested: 2026-07-23 15:26:18
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 15:26:18
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1348/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1348 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	verification verdict	843 B	↓ raw
fix.diff	suggested-fix	git-apply-able fix	602 B	view raw

VERDICT.md verdict verification verdict

↓ download raw

DF-1348 - Verification Verdict

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

Finding

Unbounded bcopy of CDB into CmdBlock[12] overflows SRB on >12-byte CDBs

Source Location

sys/dev/disk/amd/amd.c:399-400

Verdict

Source-confirmed: Unbounded bcopy of CDB into CmdBlock[12] overflows SRB on >12-byte CDB. 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: amd driver bcopy of pcsio->cdb_len into CmdBlock[12] without bound, OOB write for >12-byte CDBs. Added imin(cdb_len, sizeof(CmdBlock)). HW-gated.

Verified recommended fix

Source-confirmed: amd driver bcopy of pcsio->cdb_len into CmdBlock[12] without bound, OOB write for >12-byte CDBs. Added imin(cdb_len, sizeof(CmdBlock)). HW-gated.

Verdict

Source-confirmed: amd driver bcopy of pcsio->cdb_len into CmdBlock[12] without bound, OOB write for >12-byte CDBs. Added imin(cdb_len, sizeof(CmdBlock)). HW-gated.