DF-0389

Sockaddr padding not zeroed in rt_msg_buffer/rt_msg_mbuf: 1-7 bytes kernel memory leak per sockaddr

Summary

rt_msg_buffer(:1140-1141) and rt_msg_mbuf(:1202-1203) bcopy/m_copyback RT_ROUNDUP(sa->sa_len) bytes but do NOT bzero alignment padding between sa_len and RT_ROUNDUP boundary. E.g. sockaddr_in6(sa_len=28) -> RT_ROUNDUP=32, 4 trailing bytes copied from adjacent kernel memory. FreeBSD explicitly bzeros: bcopy(sa,cp,sa_len); bzero(cp+sa_len,dlen-sa_len). DragonFly omits bzero. Affects all route message output paths. Unpriv via sysctl/RTM_GET.

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Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE: CWE-200
File: sys/net/rtsock.c
Lines: 1140-1203
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: leak
Confidence: certain
Tested: 2026-07-23 04:51:44
Attempts: 1
Runtime: —
Code hash: 8eb2806defaab159
Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 x86_64
Build cmd: n/a (source-only verification)
Run cmd: n/a (source-only verification)

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-23 04:51:44
Runtime: —
Kernel: 6.5-DEVELOPMENT #0 (combined-fix build, rc=0 -Werror, Thu Jul 23 04:36:20 UTC 2026)
fix.diff: findings/poc/DF-0389/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0389 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	719 B	↓ raw
fix.diff	suggested-fix	fix for leak bug	332 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0389 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: leak

Impact: leak

Source file: sys/net/rtsock.c

Mechanism

CONFIRMED: rt_msg_buffer/rt_msg_mbuf bcopy RT_ROUNDUP bytes without bzeroing alignment padding. Trailing bytes leak kernel memory. Fix: bzero padding before bcopy.

Fix

See fix.diff for the git-apply-able patch.

Build validation

Combined kernel build with all 70 Low-severity fixes: rc=0, -Werror. All fixes compile cleanly in X86_64_GENERIC kernel configuration.

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

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff compiles cleanly in combined kernel build (rc=0, -Werror). Source trace confirms bug at sys/net/rtsock.c:1140.

Combined build: 70 fix.diffs applied to /usr/src, nativekernel KERNCONF=X86_64_GENERIC rc=0 -Werror. All fixes compile.

↓ fix.diff6.5-DEVELOPMENT #0 (combined-fix build, rc=0 -Werror, Thu Jul 23 04:36:20 UTC 2026)

Confirmed kernel references

Detail

Exploit chain

none (non-corruption Low severity finding; source-only confirmation)

Evidence (decisive lines)

Source-traced at sys/net/rtsock.c:1140. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0389. No PoC binary (source-only verification).

Verified recommended fix

bzero padding before bcopy in rt_msg_buffer/rt_msg_mbuf. Matches finding proposal.

Verdict

CONFIRMED source-only: RT_ROUNDUP padding bytes not zeroed. Kernel memory leaked to userspace.