mlxsw: spectrum_router: Fix use after free

In mlxsw_sp_router_fib4_add_info_destroy(), the fib_entry pointer is used
after it has been freed by mlxsw_sp_fib_entry_destroy(). Use a temporary
variable to fix this.

Fixes: 61c503f9 ("mlxsw: spectrum_router: Implement fib4 add/del switchdev obj ops")
Signed-off-by: NVincent Stehlé <vincent.stehle@laposte.net>
Cc: Jiri Pirko <jiri@mellanox.com>
Acked-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -1651,9 +1651,10 @@ static void mlxsw_sp_router_fib4_add_info_destroy(void const *data)
 	const struct mlxsw_sp_router_fib4_add_info *info = data;
 	struct mlxsw_sp_fib_entry *fib_entry = info->fib_entry;
 	struct mlxsw_sp *mlxsw_sp = info->mlxsw_sp;
+	struct mlxsw_sp_vr *vr = fib_entry->vr;
 
 	mlxsw_sp_fib_entry_destroy(fib_entry);
-	mlxsw_sp_vr_put(mlxsw_sp, fib_entry->vr);
+	mlxsw_sp_vr_put(mlxsw_sp, vr);
 	kfree(info);
 }