Subject: Re: [PATCH net-next] flow_dissector: Add IPSEC dissectors

From: Simon Horman <[email-masked]>
Date: Tue, 25 Jul 2023 21:50:43 +0200

On Tue, Jul 25, 2023 at 08:54:51AM +0530, Ratheesh Kannoth wrote:

...

> diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
> index 8664ed4fbbdf..ffec739f049a 100644
> --- a/include/net/flow_dissector.h
> +++ b/include/net/flow_dissector.h
> @@ -301,6 +301,14 @@ struct flow_dissector_key_l2tpv3 {
>  	__be32 session_id;
>  };
>  
> +/**
> + * struct flow_dissector_key_ipsec:
> + * @spi: identifier for a ipsec connection
> + */
> +struct flow_dissector_key_ipsec {
> +	__be32 spi;
> +};
> +
>  /**
>   * struct flow_dissector_key_cfm
>   * @mdl_ver: maintenance domain level (mdl) and cfm protocol version
> @@ -353,6 +361,7 @@ enum flow_dissector_key_id {
>  	FLOW_DISSECTOR_KEY_NUM_OF_VLANS, /* struct flow_dissector_key_num_of_vlans */
>  	FLOW_DISSECTOR_KEY_PPPOE, /* struct flow_dissector_key_pppoe */
>  	FLOW_DISSECTOR_KEY_L2TPV3, /* struct flow_dissector_key_l2tpv3 */
> +	FLOW_DISSECTOR_KEY_IPSEC, /* struct flow_dissector_key_ipsec */
>  	FLOW_DISSECTOR_KEY_CFM, /* struct flow_dissector_key_cfm */
>  
>  	FLOW_DISSECTOR_KEY_MAX,

...

Hi Ratheesh,

With this change, this enum now has 33 values, excluding
FLOW_DISSECTOR_KEY_MAX.  I.e the range of values is from 0 to 32.

But dissector_uses_key() looks like this:

static inline bool dissector_uses_key(const struct flow_dissector *flow_dissector,
                                      enum flow_dissector_key_id key_id)
{
        return flow_dissector->used_keys & (1 << key_id);
}

And the type of the used_keys field of struct flow_dissector
is unsigned int, a 32bit entity.

So an overflow will now occur if key_id is FLOW_DISSECTOR_KEY_CFM.

This is flagged by Sparse.

-- 
pw-bot: changes-requested