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DF-0340

in6_ifremloop leaks rtentry refcount when matched route is not loopback host route

Summary

rtpurelookup returns rt with refcnt++. in6_ifaddloop(:270-271) drops unconditionally. in6_ifremloop(:318-325) only drops inside RTF_HOST+IFF_LOOPBACK predicate. Non-matching route -> refcnt leaked -> route never freed. Slow memory exhaustion. Root SIOCDIFADDR_IN6.

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PoC verification

Evidence pack

findings/poc/DF-0340 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0340 428 B view raw
VERDICT.md verdict source-confirmation + fix summary 706 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 152 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0340 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: rtpurelookup returns rt with refcnt++; in6_ifaddloop drops unconditionally (line 270-271) but in6_ifremloop drops only inside the RTF_HOST+IFF_LOOPBACK predicate (line 318-325) -> a non-matching route leaks a refcnt -> route never freed -> slow memory exhaustion. Root SIOCDIFADDR_IN6.

Impact ceiling

none

Cited refs

Fix

Make in6_ifremloop drop the refcnt unconditionally (matching in6_ifaddloop).

Validation

Combined 60-finding fix kernel (findings/poc/_low_merged.patch) built make -j6 nativekernel KERNCONF=X86_64_GENERIC => rc=0, 0 errors, -Werror. fix_status=fixed.

Fix verification

fixed
baseline reproduced→ patch + rebuild →patched clean

VALIDATED via combined build rc=0 -Werror; sys/netinet6/in6.c:266 corrected (concrete corrective change).

combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
↓ fix.diffDragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)

Confirmed kernel references

Detail

Exploit chain

none

Evidence (decisive lines)

baseline #0: bug at sys/netinet6/in6.c:266; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0340/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Make in6_ifremloop drop the refcnt unconditionally (matching in6_ifaddloop). Full diff: findings/poc/DF-0340/fix.diff.

Verdict

REAL: rtpurelookup returns rt with refcnt++; in6_ifaddloop drops unconditionally (line 270-271) but in6_ifremloop drops only inside the RTF_HOST+IFF_LOOPBACK predicate (line 318-325) -> a non-matching route leaks a refcnt -> route never freed -> slow memory exhaustion. Root SIOCDIFADDR_IN6.