Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: af_unix: Unlink scc_entry in unix_del_edge(). Kyle Zeng reported that GC could free a dead SCC partially. The scenario is as follows: 1) Create two SCCs: X -. A <-> B ^--' 2) Run the following concurrently: 2-1) send() sk-B to sk-B from sk-X 2-2) close() both A and B At 2-1), there is a small window where unix_add_edges() publishes a new edge (B <-> B) to GC but its skb is not queued by skb_queue_tail(). If 2-2) completes before skb_queue_tail() and GC is triggered, it judges A <-> B as dead, but B is not freed because GC cannot collect the not-yet-queued skb holding the B <-> B edge. X -. A <-> B -. This edge is visible ^--' ^..' but skb is not This itself is not a problem since the next GC run will judge B as dead as well and free it finally. X -. A <.> B -. ^--' ^--' However, X's SCC forces the next GC to call unix_walk_scc_fast(), and it iterates over A through B's scc_entry. Let's unlink scc_entry before freeing the vertex in unix_del_edge().

Affected versions

Linux: 5dfd283f4651d04dbb70ceb9ae5c4a30eda3c52a through before 2b6c2842692d08e7acaf32d1eb47f95def35f3fe (git); de7921631ff323369aa63a4324695ab54ea4047e through before 6fda5c51b8e43a8440f76e65c89d9f95ddb2ef33 (git); 4090fa373f0e763c43610853d2774b5979915959 through before 1293fd69a50d188a5788b08ba3741a3e86be1608 (git); 4090fa373f0e763c43610853d2774b5979915959 through before fe198b077864feafd4aa4b33b1a5ce26f50195a2 (git); 4090fa373f0e763c43610853d2774b5979915959 through before e3702470ced94fad74d71e2232f022d2eb752a6d (git); 4090fa373f0e763c43610853d2774b5979915959 through before 594d905195024b228c962627ae5ae7c17bd582a4 (git); 6.1.141 through before 6.1.189 (semver); 6.6.93 through before 6.6.158 (semver); 6.10 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.