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 00:14:38 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Arnd Bergmann <arnd@...db.de>, alsa-devel@...a-project.org,
        Takashi Iwai <tiwai@...e.com>
Cc:     Baolin Wang <baolin.wang@...aro.org>, y2038@...ts.linaro.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 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.

[...]
> @@ -2145,14 +2202,34 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
>  		tu->qused--;
>  		spin_unlock_irq(&tu->qlock);
>  
> -		if (tu->tread) {
> -			if (copy_to_user(buffer, &tu->tqueue[qhead],
> -					 sizeof(struct snd_timer_tread)))
> +		tread = &tu->tqueue[qhead];
> +
> +		switch (tu->tread) {
> +		case TREAD_FORMAT_TIME64:
> +			if (copy_to_user(buffer, tread,
> +					 sizeof(struct snd_timer_tread64)))
>  				err = -EFAULT;
> -		} else {
> +			break;
> +		case TREAD_FORMAT_TIME32:
> +			memset(&tread32, 0, sizeof(tread32));
> +			tread32 = (struct snd_timer_tread32) {
> +				.event = tread->event,
> +				.tstamp_sec = tread->tstamp_sec,
> +				.tstamp_sec = tread->tstamp_nsec,
> +				.val = tread->val,
> +			};
> +
> +			if (copy_to_user(buffer, &tread32, sizeof(tread32)))
> +				err = -EFAULT;
> +			break;
> +		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.

Ben.

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