linux-kernel - Re: [PATCH 061/270] timekeeping: Cast raw_interval to u64 to avoid shift overflow

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Date:	Tue, 27 Nov 2012 15:08:27 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Subject: Re: [PATCH 061/270] timekeeping: Cast raw_interval to u64 to avoid
 shift overflow

On Mon, 2012-11-26 at 14:55 -0200, Herton Ronaldo Krzesinski wrote:
> 3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dan Carpenter <dan.carpenter@...cle.com>
> 
> commit 5b3900cd409466c0070b234d941650685ad0c791 upstream.
> 
> We fixed a bunch of integer overflows in timekeeping code during the 3.6
> cycle.  I did an audit based on that and found this potential overflow.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> Acked-by: John Stultz <johnstul@...ibm.com>
> Link: http://lkml.kernel.org/r/20121009071823.GA19159@elgon.mountain
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> [ herton: adapt for 3.5, timekeeper instead of tk pointer ]
> Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>

This is also missing from 3.4; looks like Herton's version is
applicable.

Ben.

> ---
>  kernel/time/timekeeping.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 63c88c1..8954990 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1012,7 +1012,7 @@ static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
>  	}
>  
>  	/* Accumulate raw time */
> -	raw_nsecs = timekeeper.raw_interval << shift;
> +	raw_nsecs = (u64)timekeeper.raw_interval << shift;
>  	raw_nsecs += timekeeper.raw_time.tv_nsec;
>  	if (raw_nsecs >= NSEC_PER_SEC) {
>  		u64 raw_secs = raw_nsecs;

-- 
Ben Hutchings
Never attribute to conspiracy what can adequately be explained by stupidity.

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