Wrong semaphore released in newblk_lookup race-avoided path — pagedep_in_progress instead of newblk_in_progress
Summary
newblk_lookup :1017 sema_get(&newblk_in_progress). Race-avoided error path :1025 sema_release(&pagedep_in_progress) — WRONG should be &newblk_in_progress. Copy-paste error not in pagedep_lookup :861 or inodedep_lookup :948 which correctly release their own semaphore. If reachable: sema_release on pagedep_in_progress not held by curthread panic or corrupt pagedep sema state. newblk_in_progress leaked held forever deadlock all subsequent newblk allocations. Currently unreachable (exclusive semaphore serializes creators no other insertion path) but latent correctness defect. Fix: sema_release(&newblk_in_progress,NULL).
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0765 · 2 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for the cited path | 388 B | view raw |
| VERDICT.md | verdict | source-confirmation narrative | 997 B | ↓ raw |
DF-0765 source-confirmation
Verdict: REPRODUCED (source-confirmed)
Impact: none Confidence: certain
Kernel ref: sys/vfs/ufs/ffs_softdep.c:1025
Mechanism
newblk_lookup race-avoided path releases &pagedep_in_progress, should be &newblk_in_progress
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: newblk_lookup race-avoided path releases &pagedep_in_progress, should be &newblk_in_progress @ sys/vfs/ufs/ffs_softdep.c:1025. 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-0765/.
Verified recommended fix
release &newblk_in_progress (not &pagedep_in_progress) on the race-avoided path. matches finding proposal. Full diff in findings/poc/DF-0765/fix.diff.
Verdict
REPRODUCED (source-confirmed). Source-trace confirmed newblk_lookup race-avoided path releases &pagedep_in_progress, should be &newblk_in_progress at sys/vfs/ufs/ffs_softdep.c:1025 against the audited sys/ tree; exact line/condition verified.
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