linux-kernel - Re: [PATCH v2 20/24] xfs: disallow broken ioctls without compat-32-bit-time

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Message-ID: <CAK8P3a10wQuHGV3c2JYSkLsKLFK8t9fOmpE=fwULe8Aj41Kshg@mail.gmail.com>
Date:   Mon, 16 Dec 2019 17:45:29 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     y2038 Mailman List <y2038@...ts.linaro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        Brian Foster <bfoster@...hat.com>,
        Dave Chinner <dchinner@...hat.com>,
        Allison Collins <allison.henderson@...cle.com>,
        Jan Kara <jack@...e.cz>, Eric Sandeen <sandeen@...deen.net>
Subject: Re: [PATCH v2 20/24] xfs: disallow broken ioctls without compat-32-bit-time

On Fri, Dec 13, 2019 at 10:05 PM Darrick J. Wong
<darrick.wong@...cle.com> wrote:
>
> On Fri, Dec 13, 2019 at 09:53:48PM +0100, Arnd Bergmann wrote:
> > When building a kernel that disables support for 32-bit time_t
> > system calls, it also makes sense to disable the old xfs_bstat
> > ioctls completely, as they truncate the timestamps to 32-bit
> > values.
>
> Note that current xfs doesn't support > 32-bit timestamps at all, so for
> now the old bulkstat/swapext ioctls will never overflow.

Right, this patch originally came after my version of the 40-bit
timestamps that I dropped from the series now.

I've added "... once the extended times are supported." above now.

> Granted, I melded everyone's suggestions into a more fully formed
> 'bigtime' feature patchset that I'll dump out soon as part of my usual
> end of year carpetbombing of the mailing list, so we likely still need
> most of this patch anyway...

What is the timeline for that work now? I'm mainly interested in
getting the removal of 'time_t/timeval/timespec' and 'get_seconds()'
from the kernel done for v5.6, but it would be good to also have
this patch and the extended timestamps in the same version
just so we can claim that "all known y2038 issues" are addressed
in that release (I'm sure we will run into bugs we don't know yet).

> > @@ -617,6 +618,23 @@ xfs_fsinumbers_fmt(
> >       return xfs_ibulk_advance(breq, sizeof(struct xfs_inogrp));
> >  }
> >
> > +/* disallow y2038-unsafe ioctls with CONFIG_COMPAT_32BIT_TIME=n */
> > +static bool xfs_have_compat_bstat_time32(unsigned int cmd)
>
> The v5 bulkstat ioctls follow an entirely separate path through
> xfs_ioctl.c, so I think you don't need the @cmd parameter.

The check is there to not forbid XFS_IOC_FSINUMBERS at
the moment, since that is not affected.

> > @@ -1815,6 +1836,11 @@ xfs_ioc_swapext(
> >       struct fd       f, tmp;
> >       int             error = 0;
> >
> > +     if (xfs_have_compat_bstat_time32(XFS_IOC_SWAPEXT)) {
>
> if (!xfs_have...()) ?

Right, fixed now.

       Arnd