Re: [PATCH net-next,v3 3/9] net: resolve forwarding path from virtual netdevice and HW destination address

[Jakub Kicinski]

On Wed, 11 Nov 2020 20:37:31 +0100 Pablo Neira Ayuso wrote:
> +int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
> +                       struct net_device_path_stack *stack)
> +{
> +     const struct net_device *last_dev;
> +     struct net_device_path_ctx ctx;
> +     struct net_device_path *path;
> +     int ret = 0;
> +
> +     memset(&ctx, 0, sizeof(ctx));
> +     ctx.dev = dev;
> +     ctx.daddr = daddr;
> +
> +     while (ctx.dev && ctx.dev->netdev_ops->ndo_fill_forward_path) {
> +             last_dev = ctx.dev;
> +
> +             path = &stack->path[stack->num_paths++];

I don't see you checking that this stack doesn't overflow.

What am I missing?

> +             ret = ctx.dev->netdev_ops->ndo_fill_forward_path(&ctx, path);
> +             if (ret < 0)
> +                     return -1;
> +
> +             if (WARN_ON_ONCE(last_dev == ctx.dev))
> +                     return -1;
> +     }
> +     path = &stack->path[stack->num_paths++];
> +     path->type = DEV_PATH_ETHERNET;
> +     path->dev = ctx.dev;
> +
> +     return ret;
> +}
> +EXPORT_SYMBOL_GPL(dev_fill_forward_path);