From: Thomas Gleixner <tglx@linutronix.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: mingo@redhat.com, levinsasha928@gmail.com,
linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org
Subject: Re: [tip:timers/core] ntp: Fix integer overflow when setting time
Date: Fri, 16 Mar 2012 10:48:02 +0100 (CET) [thread overview]
Message-ID: <alpine.LFD.2.02.1203161047220.2466@ionos> (raw)
In-Reply-To: <4F62978A.7000009@zytor.com>
On Thu, 15 Mar 2012, H. Peter Anvin wrote:
> On 03/15/2012 02:53 PM, tip-bot for Sasha Levin wrote:
> > Commit-ID: a078c6d0e6288fad6d83fb6d5edd91ddb7b6ab33
> > Gitweb: http://git.kernel.org/tip/a078c6d0e6288fad6d83fb6d5edd91ddb7b6ab33
> > Author: Sasha Levin <levinsasha928@gmail.com>
> > AuthorDate: Thu, 15 Mar 2012 12:36:14 -0400
> > Committer: Thomas Gleixner <tglx@linutronix.de>
> > CommitDate: Thu, 15 Mar 2012 21:41:34 +0100
> >
> > ntp: Fix integer overflow when setting time
> >
> > 'long secs' is passed as divisor to div_s64, which accepts a 32bit
> > divisor. On 64bit machines that value is trimmed back from 8 bytes
> > back to 4, causing a divide by zero when the number is bigger than
> > (1 << 32) - 1 and all 32 lower bits are 0.
> >
> > Use div64_long() instead.
> >
>
> Perhaps we should use the same kind of multiply-and-shift tricks we're
> doing for jiffies conversion? If nothing else it ought to perform better.
It's not a hotpath where performance matters, but divide by zero does :)
next prev parent reply other threads:[~2012-03-16 9:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 16:36 [PATCH 1/2] math: Introduce div64_long Sasha Levin
2012-03-15 16:36 ` [PATCH 2/2] ntp: Fix integer overflow when setting time Sasha Levin
2012-03-15 21:53 ` [tip:timers/core] " tip-bot for Sasha Levin
2012-03-16 1:29 ` H. Peter Anvin
2012-03-16 9:48 ` Thomas Gleixner [this message]
2012-03-16 14:42 ` H. Peter Anvin
2012-03-15 21:52 ` [tip:timers/core] math: Introduce div64_long tip-bot for Sasha Levin
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