cc)) when done.
+ *
+ * Returns the vcc pointer if valid, NULL otherwise.
+ */
+static struct atm_vcc *find_get_vcc(struct atm_vcc *vcc)
+{
+	int i;
+
+	read_lock(&vcc_sklist_lock);
+	for (i = 0; i < VCC_HTABLE_SIZE; i++) {
+		struct sock *s;
+
+		sk_for_each(s, &vcc_hash[i]) {
+			if (atm_sk(s) == vcc) {
+				sock_hold(s);
+				read_unlock(&vcc_sklist_lock);
+				return vcc;
+			}
+		}
+	}
+	read_unlock(&vcc_sklist_lock);
+	return NULL;
+}
+
 static void sigd_put_skb(struct sk_buff *skb)
 {
 	if (!sigd) {
@@ -69,7 +99,14 @@ static int sigd_send(struct atm_vcc *vcc, struct sk_buff *skb)
 
 	msg = (struct atmsvc_msg *) skb->data;
 	WARN_ON(refcount_sub_and_test(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc));
-	vcc = *(struct atm_vcc **) &msg->vcc;
+
+	vcc = find_get_vcc(*(struct atm_vcc **)&msg->vcc);
+	if (!vcc) {
+		pr_debug("invalid vcc pointer in msg\n");
+		dev_kfree_skb(skb);
+		return -EINVAL;
+	}
+
 	pr_debug("%d (0x%lx)\n", (int)msg->type, (unsigned long)vcc);
 	sk = sk_atm(vcc);
 
@@ -100,7 +137,16 @@ static int sigd_send(struct atm_vcc *vcc, struct sk_buff *skb)
 		clear_bit(ATM_VF_WAITING, &vcc->flags);
 		break;
 	case as_indicate:
-		vcc = *(struct atm_vcc **)&msg->listen_vcc;
+		/* Release the reference from msg->vcc, we'll use msg->listen_vcc instead */
+		sock_put(sk);
+
+		vcc = find_get_vcc(*(struct atm_vcc **)&msg->listen_vcc);
+		if (!vcc) {
+			pr_debug("invalid listen_vcc pointer in msg\n");
+			dev_kfree_skb(skb);
+			return -EINVAL;
+		}
+
 		sk = sk_atm(vcc);
 		pr_debug("as_indicate!!!\n");
 		lock_sock(sk);
@@ -115,6 +161,8 @@ static int sigd_send(struct atm_vcc *vcc, struct sk_buff *skb)
 		sk->sk_state_change(sk);
 as_indicate_complete:
 		release_sock(sk);
+		/* Paired with find_get_vcc(msg->listen_vcc) above */
+		sock_put(sk);
 		return 0;
 	case as_close:
 		set_bit(ATM_VF_RELEASED, &vcc->flags);
@@ -131,11 +179,15 @@ static int sigd_send(struct atm_vcc *vcc, struct sk_buff *skb)
 		break;
 	default:
 		pr_alert("bad message type %d\n", (int)msg->type);
+		/* Paired with find_get_vcc(msg->vcc) above */
+		sock_put(sk);
 		return -EINVAL;
 	}
 	sk->sk_state_change(sk);
 out:
 	dev_kfree_skb(skb);
+	/* Paired with find_get_vcc(msg->vcc) above */
+	sock_put(sk);
 	return 0;
 }
 
-- 
2.51.0[PATCH 6.19 428/781] net: atm: fix crash due to unvalidated vcc pointer in sigd_send()Greg Kroah-Hartman <gregkh@linuxfoundation.org> undefinedstable@vger.kernel.org undefined undefined undefined undefined undefined undefined¸?†™q