linux-kernel - Re: [RFC PATCH 7/7] sound: core: Avoid using timespec for struct snd_timer

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Date:   Thu, 21 Sep 2017 15:09:14 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Takashi Sakamoto <o-takashi@...amocchi.jp>,
        SF Markus Elfring <elfring@...rs.sourceforge.net>,
        Dan Carpenter <dan.carpenter@...cle.com>, jeeja.kp@...el.com,
        Vinod Koul <vinod.koul@...el.com>, dharageswari.r@...el.com,
        guneshwor.o.singh@...el.com, Bhumika Goyal <bhumirks@...il.com>,
        gudishax.kranthikumar@...el.com, Naveen M <naveen.m@...el.com>,
        hardik.t.shah@...el.com, Arvind Yadav <arvind.yadav.cs@...il.com>,
        fabf@...net.be, Mark Brown <broonie@...nel.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        alsa-devel@...a-project.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 7/7] sound: core: Avoid using timespec for struct snd_timer_tread

On Thu, Sep 21, 2017 at 8:18 AM, Baolin Wang <baolin.wang@...aro.org> wrote:

> +static int snd_timer_user_tread(void __user *argp, struct snd_timer_user *tu,
> +                               unsigned int cmd)
> +{
> +       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 __BITS_PER_LONG == 64
> +       tu->tread = xarg ? 2 : 0;
> +#ifdef IA32_EMULATION
> +       tu->tread = xarg ? 3 : 0;
> +#endif
> +#else
> +       if (cmd == SNDRV_TIMER_IOCTL_TREAD64)
> +               tu->tread = xarg ? 2 : 0;
> +       else
> +               tu->tread = xarg ? 1 : 0;
> +#endif

The 64-bit case looks broken here:

- The tread flag is different for compat and native mode, so you
   must pass a flag to identify whether you are called from
   __snd_timer_user_ioctl or from snd_timer_user_ioctl_compat().

- On x86, you have to check whether calling user space process uses
   the i386 or the x32 ABI by checking in_x32_syscall()

       Arnd