DF-0211

No negative-size guard on ccmax in clist_alloc_cblocks

Summary

ccmax signed int never checked <0. kmalloc(ccmax*sizeof(short)) with negative ccmax -> huge size_t. M_INTWAIT no M_NULLOK -> panic. Callers pass clamped positive values. 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:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L
CWE: CWE-20
File: sys/kern/tty_subr.c
Lines: 61
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 18:17:07
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: likely
Tested: 2026-07-23 18:17:07
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-0211/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0211 · 1 files

File	Type	Description	Size
fix.diff	suggested-fix	No negative-size guard on ccmax in clist_alloc_cblocks	312 B	view raw

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

fix.diff applied + combined nativekernel build rc=0 (-Werror)

fix.diff applied + combined nativekernel build rc=0 (-Werror)

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Info severity)

Evidence (decisive lines)

Source-confirmed at sys/kern/tty_subr.c:61: no negative-size guard on ccmax in clist_alloc_cblocks

Verified recommended fix

Source-confirmed at sys/kern/tty_subr.c:61: no negative-size guard on ccmax in clist_alloc_cblocks

Verdict

Source-confirmed at sys/kern/tty_subr.c:61: no negative-size guard on ccmax in clist_alloc_cblocks