netdev - Re: [PATCH net 1/2] ptp: check that rsv field is zero in struct ptp_sys_offset

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Message-Id: <20190107.091334.2284395715402499091.davem@davemloft.net>
Date:   Mon, 07 Jan 2019 09:13:34 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     mlichvar@...hat.com
Cc:     esyr@...hat.com, netdev@...r.kernel.org, richardcochran@...il.com,
        jacob.e.keller@...el.com, mtosatti@...hat.com
Subject: Re: [PATCH net 1/2] ptp: check that rsv field is zero in struct
 ptp_sys_offset_extended

From: Miroslav Lichvar <mlichvar@...hat.com>
Date: Mon, 7 Jan 2019 17:57:41 +0100

> On Mon, Jan 07, 2019 at 08:29:38AM -0800, David Miller wrote:
>> From: Eugene Syromiatnikov <esyr@...hat.com>
>> Date: Mon, 7 Jan 2019 16:22:29 +0100
>> 
>> > Otherwise it is impossible to use it for something else, as it will break
>> > userspace that puts garbage there.
>> > 
>> > The same check should be done in other structures, but the fact that
>> > data in reserved fields is ignored is already part of the kernel ABI.
>> > 
>> > Signed-off-by: Eugene Syromiatnikov <esyr@...hat.com>
>> 
>> I think the opportunity to enforce this has passed and you will break
>> userspace by doing this.
> 
> FWIW, this ioctl wasn't present in a stable Linux release yet and the
> two applications that I know that support it both zero the rsv field,
> so I think at least this patch is very unlikely to break anything.
> 
> Anyway, thanks to Eugene for catching the issues.

Oh, this ioctl went into this merge window didn't it.

Ok.  I'll keep reviewing this then.