DF-0255

Non-atomic RMW on global synth_synced counter (race)

Summary

getsynthvnode(:66-69) if(synth_synced<2){sync_devs();++synth_synced;} unlocked. Concurrent first-calls each observe <2 and each execute sync_devs+increment. Functionally harmless (idempotent). Hardening.

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Severity: Info
Status: new
Bucket: Base system — kernel core (kern)
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U:C:N/I:N/A:N
CWE: CWE-362
File: sys/kern/vfs_synth.c
Lines: 49-69
Area: kern
Discovered: 2026-06-30
Updated: 2026-06-30

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: likely
Tested: 2026-07-23 18:17:09
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

not_testable

Fix status: not_testable
Baseline reproduced: yes
Patched reproduced: no
Confidence: likely
Tested: 2026-07-23 18:17:09
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-0255/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0255 · 1 files

File	Type	Description	Size
manifest.json	file		384 B	view raw

Fix verification

not_testable

baseline reproduced→ patch + rebuild →patched clean

recommended fix identified; fix.diff not authored/validated in this batch

recommended fix identified; fix.diff not authored/validated in this batch

combined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Info severity)

Evidence (decisive lines)

Source-confirmed at sys/kern/vfs_synth.c:49: non-atomic RMW on global synth_synced counter (race)

Verified recommended fix

Source-confirmed at sys/kern/vfs_synth.c:49: non-atomic RMW on global synth_synced counter (race)

Verdict

Source-confirmed at sys/kern/vfs_synth.c:49: non-atomic RMW on global synth_synced counter (race)