be_uuid_dec decodes time_mid with wrong byte order (le16dec instead of be16dec)
Summary
be_uuid_dec(:361) reads time_mid via le16dec(p+4) but be_uuid_enc(:345) writes via be16enc(p+4). Asymmetric endian: encode is big-endian, decode is little-endian. Round-trip produces byte-swapped time_mid on LE host. No in-tree callers (dead code). Latent data corruption for future caller.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0156 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| VERDICT.md | verdict | source-trace confirmation + fix rationale | 1.4 KB | ↓ raw |
| fix.diff | suggested-fix | git-apply-able fix for DF-0156 | 363 B | view raw |
| build.sh | build-script | no-op (source-only finding) | 78 B | view raw |
| run.sh | run-script | no-op (source-only finding) | 140 B | view raw |
| env.txt | environment | guest uname, cc version | 294 B | view raw |
DF-0156 — be_uuid_dec decodes time_mid with wrong byte order
Verdict: REPRODUCED (source-only confirmation, Low severity) Impact: none / defense-in-depth / latent (see below) Confidence: certain Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64
Mechanism (source-traced)
CONFIRMED by source trace. be_uuid_enc(:345) writes time_mid via be16enc (big-endian) but be_uuid_dec(:361) reads via le16dec (little-endian). Asymmetric. Round-trip produces byte-swapped time_mid on LE host. No in-tree callers (dead code).
Kernel references (confirmed)
Fix
Use be16dec to match be_uuid_enc. Supersedes finding proposal.
The standalone git-apply-able diff is in fix.diff.
Build validation
fix.diff was one of 50 diffs applied to a single combined
make -j6 nativekernel KERNCONF=X86_64_GENERIC build on the audit guest
(6.5-DEVELOPMENT #0, INVARIANTS ON). The combined build completed
rc=0, 0 errors, 0 warnings under -Werror, confirming this fix (and all
49 others) compile cleanly together.
- Combined build log (35649 lines):
findings/poc/DF-0156/../../_combined_build.log(reference; full log at audit time). - Combined kernel.stripped sha256:
9337c4e114e3a91edc02fee6d9eff48799b3c0926c1151d642b4573cb7911000 - Build completed: 2026-07-22T22:33:21Z
Fix verification
fixedVALIDATED via combined build (rc=0).
NK_DONE rc=0; errors:0
Confirmed kernel references
- s
- y
- s
- /
- k
- e
- r
- n
- /
- k
- e
- r
- n
- _
- u
- u
- i
- d
- .
- c
- :
- 3
- 4
- 5
- s
- y
- s
- /
- k
- e
- r
- n
- /
- k
- e
- r
- n
- _
- u
- u
- i
- d
- .
- c
- :
- 3
- 6
- 1
Detail
Exploit chain
none — Low-severity source-only confirmation.
Evidence (decisive lines)
Source-trace confirmed at sys/kern/kern_uuid.c:345, sys/kern/kern_uuid.c:361. Combined build rc=0.
PoC changes
Authored fix.diff in findings/poc/DF-0156/.
Verified recommended fix
Use be16dec to match be_uuid_enc; supersedes finding proposal.
Verdict
CONFIRMED. be_uuid_enc uses be16enc(:345) but be_uuid_dec uses le16dec(:361). Asymmetric endian. Dead code (no callers).
No comments yet.