linux-kernel - Re: [PATCH v1] i40e: Add length check for IFLA_AF

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Message-ID: <20230725183652.GR11388@unreal>
Date:   Tue, 25 Jul 2023 21:36:52 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Lin Ma <linma@....edu.cn>, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, davem@...emloft.net,
        edumazet@...gle.com, pabeni@...hat.com, richardcochran@...il.com,
        ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
        john.fastabend@...il.com, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] i40e: Add length check for IFLA_AF_SPEC parsing

On Tue, Jul 25, 2023 at 09:53:27AM -0700, Jakub Kicinski wrote:
> On Tue, 25 Jul 2023 08:40:46 +0300 Leon Romanovsky wrote:
> > > Empty attributes are valid, we can't do that.  
> > 
> > Maybe Lin can add special version of nla_for_each_nested() which will
> > skip these empty NLAs, for code which don't allow empty attributes.
> 
> It's way too arbitrary. Empty attrs are 100% legit, they are called
> NLA_FLAG in policy parlance. They are basically a boolean.

I afraid that these nla_length() checks will be copied all other the
kernel without any understanding and netlink API doesn't really provide
any hint when length checks are needed and when they don't.

Thank