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.

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	1.0 KB	↓ raw
build.sh	build-script	N/A (source-only)	65 B	view raw
run.sh	run-script	N/A (source-only)	89 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 status (batch validation)

Applied with the 36 sibling fix.diffs of this batch in findings/poc/_batch41/all_fixes.patch; single in-guest make -j6 nativekernel KERNCONF=X86_64_GENERIC completed RC=0 with zero errors under -Werror (full log: findings/poc/_batch41/fix_build8.log). Behavior A/B intentionally skipped for this Info-tier item.

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