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

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Date:   Thu, 30 Aug 2018 15:09:57 +0200
From:   Guillaume Nault <g.nault@...halink.fr>
To:     Arnd Bergmann <arnd@...db.de>
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 01:54:48PM +0200, Arnd Bergmann wrote:
> 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.
> 
Sounds good. Thanks.