linux-kernel - Re: [RESEND PATCH 1/3] epoll: Extract epoll_wait_do and epoll_pwait

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Message-ID: <CAMEtUuzbFowGqSZYKH2Sej-4fq2kcQ7ALFR92=V1NcQ3c4y-YA@mail.gmail.com>
Date:	Thu, 8 Jan 2015 09:51:32 -0800
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Fam Zheng <famz@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Juri Lelli <juri.lelli@...il.com>, Zach Brown <zab@...bo.net>,
	David Drysdale <drysdale@...gle.com>,
	Kees Cook <keescook@...omium.org>,
	David Herrmann <dh.herrmann@...il.com>,
	Dario Faggioli <raistlin@...ux.it>,
	"Theodore Ts'o" <tytso@....edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Vivek Goyal <vgoyal@...hat.com>,
	Mike Frysinger <vapier@...too.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Oleg Nesterov <oleg@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Fabian Frederick <fabf@...net.be>,
	Josh Triplett <josh@...htriplett.org>,
	"David S. Miller" <davem@...emloft.net>,
	linux-fsdevel@...r.kernel.org,
	Linux API <linux-api@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Stefan Hajnoczi <stefanha@...hat.com>
Subject: Re: [RESEND PATCH 1/3] epoll: Extract epoll_wait_do and epoll_pwait_do

On Thu, Jan 8, 2015 at 1:16 AM, Fam Zheng <famz@...hat.com> wrote:
> +       if (!timeout || (timeout->tv_nsec == 0 && timeout->tv_sec == 0)) {
..
> +       } else if (timeout->tv_nsec >= 0 && timeout->tv_sec >= 0) {

the check for tv_nsec is not enough, which points
to the fragility of passing user timespec around.
I think it would be safer and cleaner to do it futex style:
  if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
      return -EFAULT;
  if (!timespec_valid(&ts))
      return -EINVAL;
  t = timespec_to_ktime(ts);
and then only pass ktime_t around.

> +               struct timespec end_time = ep_set_mstimeout(timeout);

the name is now wrong, since it's no longer MStimeout.

I think handling of compat is missing as well.
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