Merge branch 'af_unix-fix-gc-and-improve-selftest'

Michal Luczaj says:

====================
af_unix: Fix GC and improve selftest

Series deals with AF_UNIX garbage collector mishandling some in-flight
graph cycles. Embryos carrying OOB packets with SCM_RIGHTS cause issues.

Patch 1/2 fixes the memory leak.
Patch 2/2 tweaks the selftest for a better OOB coverage.

v3:
  - Patch 1/2: correct the commit message (Kuniyuki)

v2: https://lore.kernel.org/netdev/20240516145457.1206847-1-mhal@rbox.co/
  - Patch 1/2: remove WARN_ON_ONCE() (Kuniyuki)
  - Combine both patches into a series (Kuniyuki)

v1: https://lore.kernel.org/netdev/20240516103049.1132040-1-mhal@rbox.co/
====================

Link: https://lore.kernel.org/r/20240517093138.1436323-1-mhal@rbox.co
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/unix/garbage.c

@@ -342,6 +342,18 @@ enum unix_recv_queue_lock_class {
 	U_RECVQ_LOCK_EMBRYO,
 };
 
+static void unix_collect_queue(struct unix_sock *u, struct sk_buff_head *hitlist)
+{
+	skb_queue_splice_init(&u->sk.sk_receive_queue, hitlist);
+
+#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
+	if (u->oob_skb) {
+		WARN_ON_ONCE(skb_unref(u->oob_skb));
+		u->oob_skb = NULL;
+	}
+#endif
+}
+
 static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist)
 {
 	struct unix_vertex *vertex;
@@ -365,18 +377,11 @@ static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist
 
 				/* listener -> embryo order, the inversion never happens. */
 				spin_lock_nested(&embryo_queue->lock, U_RECVQ_LOCK_EMBRYO);
-				skb_queue_splice_init(embryo_queue, hitlist);
+				unix_collect_queue(unix_sk(skb->sk), hitlist);
 				spin_unlock(&embryo_queue->lock);
 			}
 		} else {
-			skb_queue_splice_init(queue, hitlist);
-
-#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
-			if (u->oob_skb) {
-				kfree_skb(u->oob_skb);
-				u->oob_skb = NULL;
-			}
-#endif
+			unix_collect_queue(u, hitlist);
 		}
 
 		spin_unlock(&queue->lock);

tools/testing/selftests/net/af_unix/scm_rights.c

@@ -197,8 +197,8 @@ void __send_fd(struct __test_metadata *_metadata,
 	       const FIXTURE_VARIANT(scm_rights) *variant,
 	       int inflight, int receiver)
 {
-#define MSG "nop"
-#define MSGLEN 3
+#define MSG "x"
+#define MSGLEN 1
 	struct {
 		struct cmsghdr cmsghdr;
 		int fd[2];