linux-kernel - Re: [PATCH] prevent timespec/timeval to ktime

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Message-ID: <20060830214441.GA21353@var.cx>
Date:	Wed, 30 Aug 2006 23:44:41 +0200
From:	Frank v Waveren <fvw@....cx>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] prevent timespec/timeval to ktime_t overflow

On Wed, Aug 30, 2006 at 10:44:28AM +0200, Thomas Gleixner wrote:
> Frank v. Waveren pointed out that on 64bit machines the timespec to
> ktime_t conversion might overflow. This is also true for timeval to
> ktime_t conversions. This breaks a "sleep inf" on 64bit machines.
...
> Check the seconds argument to the conversion and limit it to the maximum
> time which can be represented by ktime_t.

It's a solution, and it more or less fixes things without any changes
to userspace, which is nice. I still prefer my patch in
<20060827083438.GA6931@....cx> though, possibly with modifications so
it doesn't affect all timespec users but only nanosleep (we'd have to
check if the other timespec users aren't converting to ktime_t). 

With this patch, we sleep shorter than specified, and don't signal
this in any way. Returning EINVAL for anything except negative tv_sec
or invalid tv_nsec breaks the spec too, but I prefer errors to
silently sleeping too short.

I'll grant this is more of an aesthetic point than something that'll
cause real-world problems (300 years is a long time for any sleep),
but if things break I like them to do so as loudly as possible, as a
general rule.

-- 
Frank v Waveren                                  Key fingerprint: BDD7 D61E
fvw@....cx                                              5D39 CF05 4BFC F57A
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