CVE-2026-80668

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_expect: use conntrack GC to reap expectations

This patch replaces the timer API by GC worker approach for

expectations, as it already happened in many other subsystems.

Use the existing conntrack GC worker to iterate over the local list of

expectations in the master conntrack to reap expired expectations.

Check IPS_HELPER_BIT to run GC for expectations, set it on for nft_ct

expectation which nevers sets it. Hold the expectation spinlock while

iterating over the master conntrack expectation list to synchronize with

nf_ct_remove_expectations(). This also performs runtime packet path

garbage collection through the expectation insertion and lookup

functions while walking over one of the chains of the global expectation

hashtables. Unconfirmed conntrack entries are skipped since ct->ext can

be reallocated and dying are skipped since those will be gone soon.

Set on IPS_HELPER_BIT if the helper ct extension is added, then the new

GC worker does not need to bump the ct refcount to check if the ct->ext

helper is available.

This removes the extra bump on the refcount for expectation timers, this

allows to remove several nf_ct_expect_put() calls after the unlink,

after this update only refcount remains at 1 while on the expectation

hashes.

This patch implicitly addresses a race with the existing timer API

allowing an expectation to access a stale exp->master pointer which has

been already released when expectation removal loses races with an

expiring timer, ie. timer_del() reporting false.

Add a new NF_CT_EXPECT_DEAD flag to reap this expectation via GC. This

is needed by nf_conntrack_unexpect_related() which is called in error

paths to invalidate newly created expectations that has been added into

the hashes. These expectactions cannot be inmediately released as GC or

nf_ct_remove_expectations() could race to make it. On expectation

insert, the runtime GC reaps stale expectations before checking the

expectation limit set by policy.

Set current timestamp in nf_ct_expect_alloc(), then add the expectation

policy timeout (or custom timeout specified added on top of this) to

specify the expectation lifetime.