linux-kernel - Re: [PATCH net-next 1/5] pppoe: fix PPPOEIOCSFWD compat handling

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Message-ID: <CAK8P3a1WSa5yPWXYGieAc0+Xk=CAy_G-RhNNcQBsGQGOU-8WfA@mail.gmail.com>
Date:   Thu, 30 Aug 2018 13:54:48 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     g.nault@...halink.fr
Cc:     Paul Mackerras <paulus@...ba.org>, linux-ppp@...r.kernel.org,
        Networking <netdev@...r.kernel.org>, mitch@...oth.com,
        mostrows@...thlink.net, jchapman@...alix.com, xeb@...l.ru,
        David Miller <davem@...emloft.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 1/5] pppoe: fix PPPOEIOCSFWD compat handling

On Thu, Aug 30, 2018 at 1:04 PM Guillaume Nault <g.nault@...halink.fr> wrote:
>
> On Wed, Aug 29, 2018 at 04:03:26PM +0200, Arnd Bergmann wrote:
> > Support for handling the PPPOEIOCSFWD ioctl in compat mode was added in
> > linux-2.5.69 along with hundreds of other commands, but was always broken
> > sincen only the structure is compatible, but the command number is not,
> > due to the size being sizeof(size_t), or at first sizeof(sizeof((struct
> > sockaddr_pppox)), which is different on 64-bit architectures.
> >
> And the implementation was broken until 2016 (see 29e73269aa4d ("pppoe:
> fix reference counting in PPPoE proxy")), and nobody ever noticed. I
> should probably have removed this ioctl entirely instead of fixing it.
> Clearly, it has never been used.
>
> If you think it's worth fixing (as opposed to dropping this ioctl or
> its compat mode), then,
> Acked-by: Guillaume Nault <g.nault@...halink.fr>

I don't care much, but fixing it seems seems easier than coming
up with a convincing rationale for dropping.

I'll update the changelog text to include your additional background
information though, unless someone else prefers to have it dropped.

       Arnd