Summary

xdisk.c:601-604 DMSG_DBG_SHELL|REPLY handler kprintf(aux_data) at level 0 with xa_debug default=1 so always printed. No auth: any xdisk server peer can send DBG_SHELL|REPLY on any open circuit. No rate limit, no size cap (DMSG_AUX_MAX=1MB). Attacker floods kernel console/msgbuf with arbitrary text -> serial console DoS + log eviction. Remote via untrusted network disk server. Fix: gate behind xa_debug>=2 + truncate to 128 bytes.

PoC verification

Evidence pack

findings/poc/DF-1572 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	407 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-1572 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: xdisk.c:601-604 DMSG_DBG_SHELL|REPLY handler kprintf(aux_data) at level 0 with xa_debug default=1 so always printed. No auth: any xdisk server peer can send DBG_SHELL|REPLY on any open circuit. No rat

Citation: sys/dev/disk/xdisk/xdisk.c:592-605

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: DMSG_DBG_SHELL reply logs attacker string to console unconditionally (xdisk.c:601-604)

Verified recommended fix

Source-confirmed: DMSG_DBG_SHELL reply logs attacker string to console unconditionally (xdisk.c:601-604)

Verdict