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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 13 Dec 2019 11:25:40 +0100
Message-ID: <CAK8P3a2BwA-wnxRPLgLrb9e2HpnrhXXyNyLfn4sOpSOjiJ3oEw@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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Sender: linux-kernel-owner@vger.kernel.org
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On Thu, Dec 12, 2019 at 3:27 PM Ben Hutchings
<ben.hutchings@codethink.co.uk> wrote:
> 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@codethink.co.uk> wrote:
> > > On Wed, 2019-12-11 at 22:20 +0100, Arnd Bergmann wrote:
> > > > @@ -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.

This is what I added now:

--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -2161,6 +2161,7 @@ static ssize_t snd_timer_user_read(struct file
*file, char __user *buffer,
                unit = sizeof(struct snd_timer_read);
                break;
        default:
+               WARN_ONCE(1, "Corrupt snd_timer_user\n");
                return -ENOTSUPP;
        }

         Arnd