netdev - Re: [net-next v3 1/6] net: dcb: add new pcp selector to app object

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Date:   Wed, 26 Oct 2022 16:51:32 +0200
From:   Petr Machata <petrm@...dia.com>
To:     <Daniel.Machon@...rochip.com>
CC:     <petrm@...dia.com>, <netdev@...r.kernel.org>,
        <davem@...emloft.net>, <maxime.chevallier@...tlin.com>,
        <thomas.petazzoni@...tlin.com>, <edumazet@...gle.com>,
        <kuba@...nel.org>, <pabeni@...hat.com>,
        <Lars.Povlsen@...rochip.com>, <Steen.Hegelund@...rochip.com>,
        <UNGLinuxDriver@...rochip.com>, <joe@...ches.com>,
        <linux@...linux.org.uk>, <Horatiu.Vultur@...rochip.com>,
        <Julia.Lawall@...ia.fr>, <vladimir.oltean@....com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [net-next v3 1/6] net: dcb: add new pcp selector to app object


<Daniel.Machon@...rochip.com> writes:

>> I'm missing a validation that DCB_APP_SEL_PCP is always sent in
>> DCB_ATTR_DCB_APP encapsulation. Wouldn't the current code permit
>> sending it in the IEEE encap? This should be forbidden.
>
> Right. Current impl. does not check that the non-std selectors received, are
> sent with a DCB_ATTR_DCB_APP type.  We could introduce a new check
> dcbnl_app_attr_selector_validate() that checks combination of type and 
> selector, after the type and nla_len(attr) has been checked, so that:
>
>  validate type -> validate nla_len(attr) -> validate selector

This needs to be validated, otherwise there's no point in having a
dedicated attribute for the non-standard stuff.

>> And vice versa: I'm not sure we want to permit sending the standard
>> attributes in the DCB encap.
>
> dcbnl_app_attr_type_get() in dcbnl_ieee_fill() takes care of this. IEEE are
> always sent in DCB_ATTR_IEEE and non-std are sent in DCB_ATTR_DCB.

By "sending" I meant userspace sending this to the kernel. So bounce
extended opcodes that are wrapped in IEEE and bounce IEEE opcodes
wrapped in DCB as well.