Summary

afd_sense L383/395/408 stores device-supplied blocksize verbatim no zero check returns 0 success. afd_attach L109-113 L130 calls afd_describe. afd_describe L459-462 if(bootverbose) fdp->mediasize/fdp->sectorsize. sectorsize==0 from READ CAPACITY/MODE SENSE -> 0/0 #DE kernel panic at attach. Only reached with bootverbose (-v). Local attacker physical USB ATAPI floppy emulator returning blocksize=0. Same pattern ata-disk.c/ata-lowlevel.c. Fix: sectorsize ?:512 fallback + guard if(sectorsize&&sectors&&heads) in describe.

PoC verification

Evidence pack

findings/poc/DF-1945 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	616 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-1945 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: afd_sense L383/395/408 stores device-supplied blocksize verbatim no zero check returns 0 success. afd_attach L109-113 L130 calls afd_describe. afd_describe L459-462 if(bootverbose) fdp->mediasize/fdp-

Citation: sys/dev/disk/nata/atapi-fd.c:383-462

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: mediasize/sectorsize div-by-zero when sectorsize=0 (atapi-fd.c:459-462)

Verified recommended fix

Source-confirmed: mediasize/sectorsize div-by-zero when sectorsize=0 (atapi-fd.c:459-462)

Verdict