net: macsec: fix net device access prior to holding a lock

Currently macsec offload selection update routine accesses
the net device prior to holding the relevant lock.
Fix by holding the lock prior to the device access.

Fixes: dcb780fb ("net: macsec: add nla support for changing the offloading selection")
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
Link: https://lore.kernel.org/r/20221211075532.28099-1-ehakim@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/macsec.c

@@ -2593,7 +2593,7 @@ static int macsec_upd_offload(struct sk_buff *skb, struct genl_info *info)
 	const struct macsec_ops *ops;
 	struct macsec_context ctx;
 	struct macsec_dev *macsec;
-	int ret;
+	int ret = 0;
 
 	if (!attrs[MACSEC_ATTR_IFINDEX])
 		return -EINVAL;
@@ -2606,28 +2606,36 @@ static int macsec_upd_offload(struct sk_buff *skb, struct genl_info *info)
 					macsec_genl_offload_policy, NULL))
 		return -EINVAL;
 
+	rtnl_lock();
+
 	dev = get_dev_from_nl(genl_info_net(info), attrs);
-	if (IS_ERR(dev))
-		return PTR_ERR(dev);
+	if (IS_ERR(dev)) {
+		ret = PTR_ERR(dev);
+		goto out;
+	}
 	macsec = macsec_priv(dev);
 
-	if (!tb_offload[MACSEC_OFFLOAD_ATTR_TYPE])
-		return -EINVAL;
+	if (!tb_offload[MACSEC_OFFLOAD_ATTR_TYPE]) {
+		ret = -EINVAL;
+		goto out;
+	}
 
 	offload = nla_get_u8(tb_offload[MACSEC_OFFLOAD_ATTR_TYPE]);
 	if (macsec->offload == offload)
-		return 0;
+		goto out;
 
 	/* Check if the offloading mode is supported by the underlying layers */
 	if (offload != MACSEC_OFFLOAD_OFF &&
-	    !macsec_check_offload(offload, macsec))
-		return -EOPNOTSUPP;
+	    !macsec_check_offload(offload, macsec)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
 
 	/* Check if the net device is busy. */
-	if (netif_running(dev))
-		return -EBUSY;
-
-	rtnl_lock();
+	if (netif_running(dev)) {
+		ret = -EBUSY;
+		goto out;
+	}
 
 	prev_offload = macsec->offload;
 	macsec->offload = offload;
@@ -2662,7 +2670,7 @@ static int macsec_upd_offload(struct sk_buff *skb, struct genl_info *info)
 
 rollback:
 	macsec->offload = prev_offload;
-
+out:
 	rtnl_unlock();
 	return ret;
 }