DF-2049

No synchronization: concurrent LOADTEST frees tbridge_testcase out from under running test kthread (UAF)

Summary

tbridge_dev_ioctl (240-304) manipulates module-globals tbridge_curtest/testcase/msgbuf_ptr/remsz/result_ready with NO mutex/token/serializer and no per-fd state. Two concurrent ioctls race: TBRIDGE_LOADTEST while another thread in GETRESULT calls tbridge_reset (208-221) which prop_object_release(tbridge_testcase) freeing the dict that running kthread and in-flight GETRESULT still deref via testcase_get_name/set_result/get_timeout -> UAF. Also lost-wakeup TOCTOU between !tbridge_result_ready check (272) and tsleep(273) no tsleep_interlock/PINTERLOCKED -> test finishing just before tsleep blocks until timeout aborts spuriously. Two root fds /dev/tbridge. AV:L/AC:H/PR:H, I:H/A:H.

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U:C:N/I:H/A:H
CWE: CWE-362
File: sys/dev/misc/tbridge/tbridge.c
Lines: 240-304
Area: dev
Discovered: 2026-07-23
Updated: 2026-07-23

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-25 10:25:19
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: certain
Tested: 2026-07-25 10:25:19
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-2049/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-2049 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-2049	659 B	↓ raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-2049

↓ download raw

DF-2049 Verification Verdict

Severity: Low Impact class: uaf Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: No synchronization on tbridge globals (needs mutex; documented, not applied)

Fix identified but complex multi-line change not applied to batch kernel build.

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

not_testable

baseline reproduced→ patch + rebuild →patched clean

Fix identified in VERDICT.md but too complex for standalone patch; HW/module/runtime-gated, no runtime PoC re-test possible on guest.

Fix identified in VERDICT.md but too complex for standalone patch; HW/module/runtime-gated, no runtime PoC re-test possible on guest.

combined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): tbridge_dev_ioctl manipulates module-globals tbridge_curtest/testcase/msgbuf_ptr/remsz/result_ready with NO mutex/token/serializer and no per-fd state; concurrent ioctls race

Verified recommended fix

REPRODUCED (source-only): tbridge_dev_ioctl manipulates module-globals tbridge_curtest/testcase/msgbuf_ptr/remsz/result_ready with NO mutex/token/serializer and no per-fd state; concurrent ioctls race -> corruption/UAF.