netdev - Re: [PATCH net-next 2/6] net: sched: Add centralized RED flag checking

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Message-ID: <87sgigy1zr.fsf@mellanox.com>
Date:   Tue, 10 Mar 2020 10:48:24 +0100
From:   Petr Machata <petrm@...lanox.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org,
        davem@...emloft.net, jiri@...lanox.com, jhs@...atatu.com,
        xiyou.wangcong@...il.com, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net-next 2/6] net: sched: Add centralized RED flag checking


Jakub Kicinski <kuba@...nel.org> writes:

> On Mon,  9 Mar 2020 20:34:59 +0200 Ido Schimmel wrote:
>> From: Petr Machata <petrm@...lanox.com>
>> 
>> The qdiscs RED, GRED, SFQ and CHOKE use different subsets of the same pool
>> of global RED flags. Add a common function for all of these to validate
>> that only supported flags are passed. In later patches this function will
>> be extended with a check for flag compatibility / meaningfulness.
>> 
>> Signed-off-by: Petr Machata <petrm@...lanox.com>
>> Acked-by: Jiri Pirko <jiri@...lanox.com>
>> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
>
> The commit message should mention this changes behavior of the kernel,
> as the flags weren't validated, so buggy user space may start to see
> errors.

True, I can add that for v2.

> The only flags which are validated today are the gRED per-vq ones, which
> are a recent addition and were validated from day one.

Do you consider the validation as such to be a problem? Because that
would mean that the qdiscs that have not validated flags this way
basically cannot be extended ever ("a buggy userspace used to get a
quiet slicing of flags, and now they mean something").