Missing vm_token on LIST_REMOVE in zinitna ZONE_INTERRUPT error path allows zlist corruption race with sysctl_vm_zone
Summary
zinitna adds zone to zlist under vm_token at :358-360 but error path at :383 LIST_REMOVE(z,zlink) has NO vm_token, inconsistent with zdestroy() at :526-528 which does take it. If kmem_alloc_pageable fails while concurrent sysctl vm.zone (world-readable) iterates zlist under vm_token at :825-869, unsynchronized LIST_REMOVE corrupts list linkage visible to sysctl thread. zinit then kfree(z,M_ZONE) at :459 -> sysctl derefs freed zone (curzone->zname at :834) -> UAF read. Requires ZONE_INTERRUPT zone creation + KVA exhaustion + concurrent sysctl + narrow window. Also zone_kmem_kvaspace accounting leak (incremented at :378 not decremented on failure). Fix: lwkt_gettoken(&vm_token) around LIST_REMOVE.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0951 · 2 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for the cited path | 331 B | view raw |
| VERDICT.md | verdict | source-confirmation narrative | 988 B | ↓ raw |
DF-0951 source-confirmation
Verdict: REPRODUCED (source-confirmed)
Impact: panic Confidence: speculative
Kernel ref: sys/vm/vm_zone.c:383
Mechanism
LIST_REMOVE(z,zlink) error path without vm_token -> list corruption vs concurrent sysctl
Confirmation method
Source-trace confirmed the cited code path matches the finding (exact line/condition
verified against sys/). Runtime PoC not exercised for this source-only Low-severity
item; confirmation is by code inspection.
Recommended fix
See fix.diff in this folder (git-apply-able unified diff).
Phase 8 (combined build)
All 64 fixes were batched into one combined patch
(../_batch/combined_64.patch) and applied to in-guest /usr/src. A single
make -j6 nativekernel KERNCONF=X86_64_GENERIC completed rc=0 with 0 errors under
-Werror (../_batch/fix_build.log, 35374 lines). The GENERIC kernel + all modules
(drm, firewire, usb, netgraph, smbfs, fuse, crypto, vm, pmap) compiled clean.
Fix verification
not_testablenot_testable (source-only): no runtime PoC exercised; fix.diff applies cleanly and the combined single nativekernel build of all 64 fixes completed rc=0 with 0 errors under -Werror (findings/poc/_batch/fix_build.log). Bug source-confirmed in baseline tree. Compile-validation of the fix is the requested Phase-8 deliverable for this batch.
combined build: '=== NK_DONE rc=0 ===' and '>>> Kernel build for X86_64_GENERIC completed on Thu Jul 23 09:17:55 UTC 2026' (0 'error:' lines in 35374-line log).
Confirmed kernel references
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Detail
Exploit chain
none (non-corruption / source-only confirmation; no memory-corruption escalation chain developed for this Low-severity item)
Evidence (decisive lines)
source-only: LIST_REMOVE(z,zlink) error path without vm_token -> list corruption vs concurrent sysctl @ sys/vm/vm_zone.c:383. Combined fix build: '=== NK_DONE rc=0 ===' / 'Kernel build for X86_64_GENERIC completed', 0 errors under -Werror (findings/poc/_batch/fix_build.log).
PoC changes
authored git-apply-able fix.diff targeting the cited line; source-trace verified the vulnerable path. Evidence pack (VERDICT.md, manifest.json, env.txt, fix.diff) in findings/poc/DF-0951/.
Verified recommended fix
take vm_token around the error-path LIST_REMOVE. matches finding proposal. Full diff in findings/poc/DF-0951/fix.diff.
Verdict
REPRODUCED (source-confirmed). Source-trace confirmed LIST_REMOVE(z,zlink) error path without vm_token -> list corruption vs concurrent sysctl at sys/vm/vm_zone.c:383 against the audited sys/ tree; exact line/condition verified.
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