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DF-0298

ng_type->refs refcount mutated without typelist lock

Summary

ng_make_node_common(:636) refs++ and ng_unref_node(:763) refs-- with NO lock (author XXX maybe should get types lock?). ng_rmtype/MOD_UNLOAD check refs>1/==0 also unlocked. Lost update -> module freed while node still references type vtable -> UAF on next rcvmsg/rcvdata. Root-only.

Discussion (0)

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PoC verification

Evidence pack

findings/poc/DF-0298 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0298 693 B view raw
VERDICT.md verdict source-confirmation + fix summary 657 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 139 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0298 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: ng_make_node_common increments node->refs/type->refs with no lock (author XXX); ng_rmtype/MOD_UNLOAD check refs unlocked -> lost update -> type vtable freed while a node still references it -> UAF. Root-only (netgraph).

Impact ceiling

none

Cited refs

Fix

Guard the refs++ and the undo decrement with crit_enter()/crit_exit() (matches ng_unref's existing crit).

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/netgraph/netgraph/ng_base.c:398 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/netgraph/netgraph/ng_base.c:398; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0298/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Guard the refs++ and the undo decrement with crit_enter()/crit_exit() (matches ng_unref's existing crit). Full diff: findings/poc/DF-0298/fix.diff.

Verdict

REAL: ng_make_node_common increments node->refs/type->refs with no lock (author XXX); ng_rmtype/MOD_UNLOAD check refs unlocked -> lost update -> type vtable freed while a node still references it -> UAF. Root-only (netgraph).