linux-kernel - Re: [Y2038] [PATCH v7 6/9] ALSA: Avoid using timespec for struct snd_timer

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Date:   Thu, 12 Dec 2019 14:27:06 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     ALSA Development Mailing List <alsa-devel@...a-project.org>,
        Takashi Iwai <tiwai@...e.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Mark Brown <broonie@...nel.org>,
        Baolin Wang <baolin.wang7@...il.com>
Subject: Re: [Y2038] [PATCH v7 6/9] ALSA: Avoid using timespec for struct
 snd_timer_tread

On Thu, 2019-12-12 at 10:57 +0100, Arnd Bergmann wrote:
> On Thu, Dec 12, 2019 at 1:14 AM Ben Hutchings
> <ben.hutchings@...ethink.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.

Yes, WARN_ON() or WARN_ON_ONCE() would make sense.

Ben.

-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom