DF-2050

tsleep timeout computed as hz * user-controlled int32 can overflow or go negative

Summary

tsleep timeout at tbridge.c:274 "hz * testcase_get_timeout(tbridge_testcase)". hz is int (kernel.h:81); testcase_get_timeout returns user-supplied int32 read verbatim from prop dict (90-101) no clamping. Product signed-int multiply overflows for large magnitudes (hz=100 timeout=INT32_MAX/100); straightforwardly negative for negative timeout. tsleep only checks if(timo) (kern_synch.c:691) so nonzero negative reaches _callout_setup_quick with negative tick -> immediate spurious EWOULDBLOCK -> tb_abort/tbridge_test_done(RESULT_TIMEOUT) while test still running. AV:L/PR:H/AC:L, A:L.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U:C:N/I:N/A:L
CWE: CWE-190
File: sys/dev/misc/tbridge/tbridge.c
Lines: 274
Area: dev
Discovered: 2026-07-23
Updated: 2026-07-23

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: dos
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

fixed

Fix status: fixed
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-2050/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-2050 · 3 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-2050	617 B	↓ raw
fix.diff	suggested-fix	Clamp tsleep timeout to prevent hz*int32 overflow	1010 B	view 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-2050

↓ download raw

DF-2050 Verification Verdict

Severity: Low Impact class: dos 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: Clamp tsleep timeout to prevent hz*int32 overflow

Fix applied and validated in batch kernel build (rc=0, -Werror).

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

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): tbridge tsleep timeout = hz * testcase_get_timeout(tbridge_testcase); hz is int; testcase_get_timeout returns user-supplied int32 no clamping; product signed-overflows; huge/

Verified recommended fix

REPRODUCED (source-only): tbridge tsleep timeout = hz * testcase_get_timeout(tbridge_testcase); hz is int; testcase_get_timeout returns user-supplied int32 no clamping; product signed-overflows; huge/negative timeout -> indefinite hang.