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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 12 Dec 2019 10:57:08 +0100
Message-ID: <CAK8P3a2-5qNsy0cbxmLYfgwtbdSp4e4XXQ+gAAh0X+Kr1F-4sw@mail.gmail.com>
Subject: Re: [Y2038] [PATCH v7 6/9] ALSA: Avoid using timespec for struct snd_timer_tread
To:     Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc:     ALSA Development Mailing List <alsa-devel@alsa-project.org>,
        Takashi Iwai <tiwai@suse.com>,
        Baolin Wang <baolin.wang@linaro.org>,
        y2038 Mailman List <y2038@lists.linaro.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Mark Brown <broonie@kernel.org>,
        Baolin Wang <baolin.wang7@gmail.com>
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On Thu, Dec 12, 2019 at 1:14 AM Ben Hutchings
<ben.hutchings@codethink.co.uk> wrote:
>
> On Wed, 2019-12-11 at 22:20 +0100, Arnd Bergmann wrote:
> [...]
> > +static int snd_timer_user_tread(void __user *argp, struct snd_timer_user *tu,
> > +                             unsigned int cmd, bool compat)
> > +{
> > +     int __user *p = argp;
> > +     int xarg, old_tread;
> > +
> > +     if (tu->timeri) /* too late */
> > +             return -EBUSY;
> > +     if (get_user(xarg, p))
> > +             return -EFAULT;
> > +
> > +     old_tread = tu->tread;
> > +
> > +     if (!xarg)
> > +             tu->tread = TREAD_FORMAT_NONE;
> > +     else if (cmd == SNDRV_TIMER_IOCTL_TREAD64 ||
> > +              (IS_ENABLED(CONFIG_64BITS) && !compat))
>
> This needs to check for CONFIG_64BIT not CONFIG_64BITS.

Fixed now, good catch!

> > @@ -2145,14 +2202,34 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
> > +             case TREAD_FORMAT_NONE:
> >                       if (copy_to_user(buffer, &tu->queue[qhead],
> >                                        sizeof(struct snd_timer_read)))
> >                               err = -EFAULT;
> > +                     break;
> > +             default:
> > +                     err = -ENOTSUPP;
> [...]
>
> This is not a valid error code for returning to user-space, but this
> case should be impossible so I don't think it matters.

Agreed. Maybe it should also WARN_ON(1), as there getting here
would indicate a bug in the kernel.

    Arnd