net/mlx5e: Fix slab-out-of-bounds in mlx5e_rep_is_lag_netdev

mlx5e_rep_is_lag_netdev is used as first check as part of netdev events
handler for bond device of non-uplink representors, this handler can get
any netdevice under the same network namespace of mlx5e netdevice. Current
code treats the netdev as mlx5e netdev and only later on verifies this,
hence causes the following Kasan trace:
[15402.744990] ==================================================================
[15402.746942] BUG: KASAN: slab-out-of-bounds in mlx5e_rep_is_lag_netdev+0xcb/0xf0 [mlx5_core]
[15402.749009] Read of size 8 at addr ffff880391f3f6b0 by task ovs-vswitchd/5347

[15402.752065] CPU: 7 PID: 5347 Comm: ovs-vswitchd Kdump: loaded Tainted: G    B      O     --------- -t - 4.18.0-g3dcc204d291d-dirty #1
[15402.755349] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
[15402.757600] Call Trace:
[15402.758968]  dump_stack+0x71/0xab
[15402.760427]  print_address_description+0x6a/0x270
[15402.761969]  kasan_report+0x179/0x2d0
[15402.763445]  ? mlx5e_rep_is_lag_netdev+0xcb/0xf0 [mlx5_core]
[15402.765121]  mlx5e_rep_is_lag_netdev+0xcb/0xf0 [mlx5_core]
[15402.766782]  mlx5e_rep_esw_bond_netevent+0x129/0x620 [mlx5_core]

Fix by deferring the violating access to be post the netdev verify check.

Fixes: 7e51891 ("net/mlx5e: Use netdev events to set/del egress acl forward-to-vport rule")
Signed-off-by: Raed Salem <[email protected]>
Reviewed-by: Roi Dayan <[email protected]>
Reviewed-by: Vu Pham <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: Raed Salem

drivers/net/ethernet/mellanox/mlx5/core/en/rep/bond.c

@@ -183,13 +183,16 @@ void mlx5e_rep_bond_unslave(struct mlx5_eswitch *esw,
 
 static bool mlx5e_rep_is_lag_netdev(struct net_device *netdev)
 {
-	struct mlx5e_priv *priv = netdev_priv(netdev);
-	struct mlx5e_rep_priv *rpriv = priv->ppriv;
+	struct mlx5e_rep_priv *rpriv;
+	struct mlx5e_priv *priv;
 
 	/* A given netdev is not a representor or not a slave of LAG configuration */
 	if (!mlx5e_eswitch_rep(netdev) || !bond_slave_get_rtnl(netdev))
 		return false;
 
+	priv = netdev_priv(netdev);
+	rpriv = priv->ppriv;
+
 	/* Egress acl forward to vport is supported only non-uplink representor */
 	return rpriv->rep->vport != MLX5_VPORT_UPLINK;
 }