linux-kernel - Re: [RFC PATCH 5/9] ntsync: Introduce NTSYNC_IOC_WAIT

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Date: Wed, 24 Jan 2024 12:02:32 -0600
From: Elizabeth Figura <zfigura@...eweavers.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
 Arnd Bergmann <arnd@...db.de>
Cc: wine-devel@...ehq.org,
 André Almeida <andrealmeid@...lia.com>,
 Wolfram Sang <wsa@...nel.org>, Arkadiusz Hiler <ahiler@...eweavers.com>,
 Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC PATCH 5/9] ntsync: Introduce NTSYNC_IOC_WAIT_ANY.

On Wednesday, 24 January 2024 01:56:52 CST Arnd Bergmann wrote:
> On Wed, Jan 24, 2024, at 01:40, Elizabeth Figura wrote:
> 
> > +	if (args->timeout) {
> > +		struct timespec64 to;
> > +
> > +		if (get_timespec64(&to, u64_to_user_ptr(args->timeout)))
> > +			return -EFAULT;
> > +		if (!timespec64_valid(&to))
> > +			return -EINVAL;
> > +
> > +		timeout = timespec64_to_ns(&to);
> > +	}
> 
> Have you considered just passing the nanosecond value here?
> Since you do not appear to write it back, that would avoid
> the complexities of dealing with timespec layout differences
> and indirection.

That'd be nicer in general. I think there was some documentation that advised
using timespec64 for new ioctl interfaces but it may have been outdated or
misread.

> 
> > +	ids = kmalloc_array(count, sizeof(*ids), GFP_KERNEL);
> > +	if (!ids)
> > +		return -ENOMEM;
> > +	if (copy_from_user(ids, u64_to_user_ptr(args->objs),
> > +			   array_size(count, sizeof(*ids)))) {
> > +		kfree(ids);
> > +		return -EFAULT;
> > +	}
> 
> This looks like memdup_user() would be slightly simpler.

That's useful, thanks.