Summary

ipmi_kcs_probe_align L527/536/566/573/586/594 while(status&KCS_STATUS_IBF){DELAY(100);status=INB(KCS_CTL_STS);} and while(!(status&KCS_STATUS_OBF)) loops lack the ticks-start<MAX_TIMEOUT guard that kcs_wait_for_ibf/obf L60/66/83/89 use. Invoked from PCI/ISA attach during autoconf config_intrhook. Malicious PCIe IPMI card or supply-chain BMC firmware compromise or buggy BMC that never clears IBF/never asserts OBF -> boot never completes kernel wedged at device-probe phase. Fix: route all flag polling through kcs_wait_for_ibf/obf or add ticks-start<MAX_TIMEOUT guard inline.

PoC verification

Evidence pack

findings/poc/DF-1866 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	511 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-1866 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: ipmi_kcs_probe_align L527/536/566/573/586/594 while(status&KCS_STATUS_IBF){DELAY(100);status=INB(KCS_CTL_STS);} and while(!(status&KCS_STATUS_OBF)) loops lack the ticks-start<MAX_TIMEOUT guard that kc

Citation: sys/dev/misc/ipmi/ipmi_kcs.c:527-595

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: unbounded IBF/OBF polling loops in probe_align (ipmi_kcs.c:527-595)

Verified recommended fix

Source-confirmed: unbounded IBF/OBF polling loops in probe_align (ipmi_kcs.c:527-595)

Verdict