DF-1958

Unclamped csio->cdb_len and csio->sense_len allow OOB read of cdb_bytes and OOB write of sense_data in vpo_intr

Summary

vpo_intr L220-228 forwards csio->cdb_len and csio->sense_len to imm_do_scsi/vpoio_do_scsi without clamping to inline buffer sizes: cdb_bytes[IOCDBLEN=16] cam_ccb.h:587 sense_data[SSD_FULL_SIZE=32] scsi_all.h. Send loop vpoio.c:715 for(k=0;k<clen;k++) reads &command[k] k=0..254 reading 239 bytes adjacent csio fields (cdb_io.cdb_ptr union msg_ptr kernel pointer). Receive loop vpoio.c:741/757 writes buffer[0..count-1] bounded by blen=255 not buffer size 32 -> 223 bytes OOB write into sense_len/cdb_len/sglist_cnt/scsi_status/sense_resid/resid/cdb_io/msg_ptr/msg_len/tag_action/tag_id/init_id. Same pattern DF-1088(pass)/DF-1510/DF-1546/DF-1547. Priv-gated root-only /dev/passN SYSCAP_RESTRICTEDROOT scsi_pass.c:308; sg caps IOCDBLEN scsi_sg.c:507; periphs sense_len=SSD_FULL_SIZE. Malicious parallel-port SCSI target returns >32 bytes sense -> OOB write attacker-controlled. Fix: clamp cdb_len<=sizeof(cdb_bytes) sense_len<=sizeof(sense_data) at vpo_intr entry.

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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:H/PR:H/UI:N/S:U:C:L/I:L/A:L
CWE: CWE-129
File: sys/dev/disk/vpo/vpo.c
Lines: 220-284
Area: dev
Discovered: 2026-07-21
Updated: 2026-07-21

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: likely
Tested: 2026-07-23 17:00:17
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 17:00:18
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1958/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1958 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	779 B	view raw
VERDICT.md	verdict	source-confirmation analysis	702 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-1958 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: vpo_intr L220-228 forwards csio->cdb_len and csio->sense_len to imm_do_scsi/vpoio_do_scsi without clamping to inline buffer sizes: cdb_bytes[IOCDBLEN=16] cam_ccb.h:587 sense_data[SSD_FULL_SIZE=32] scs

Citation: sys/dev/disk/vpo/vpo.c:220-284

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: unclamped csio->cdb_len OOB reads cdb_bytes (vpo.c:220-284)

Verified recommended fix

Source-confirmed: unclamped csio->cdb_len OOB reads cdb_bytes (vpo.c:220-284)

Verdict

Source-confirmed: unclamped csio->cdb_len OOB reads cdb_bytes (vpo.c:220-284)