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From: Dave Chinner <david@fromorbit.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ben Myers <bpm@sgi.com>, Alex Elder <elder@kernel.org>,
	kernel-janitors@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [patch] xfs: bug widening binary "not" operation
Date: Thu, 16 May 2013 23:03:14 +0000	[thread overview]
Message-ID: <20130516230314.GH24635@dastard> (raw)
In-Reply-To: <20130516075330.GB7494@elgon.mountain>

On Thu, May 16, 2013 at 10:53:30AM +0300, Dan Carpenter wrote:
> The problem here is:
> 
> 	ioffset = offset & ~(rounding - 1);
> 
> "offset" and "ioffset" are type xfs_off_t (__s64) and "rounding" is
> unsigned int.  The "offset & ~(rounding - 1)" clears the high 32 bits
> and which is unintentional.
> 
> This is a static checker fix so I'm not sure how much difference this
> makes in real life.

It is a real problem, but one that is masked by the way we do range
flushing right now.

As it is, the static checker missed the:

	rounding = max_t(uint, ....);

The line before the above usage. I posted a patch to fix this this
2 weeks ago here:

http://oss.sgi.com/pipermail/xfs/2013-May/025986.html

But thanks for the independent confirmation of the problem, Dan. ;)

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ben Myers <bpm@sgi.com>, Alex Elder <elder@kernel.org>,
	kernel-janitors@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [patch] xfs: bug widening binary "not" operation
Date: Fri, 17 May 2013 09:03:14 +1000	[thread overview]
Message-ID: <20130516230314.GH24635@dastard> (raw)
In-Reply-To: <20130516075330.GB7494@elgon.mountain>

On Thu, May 16, 2013 at 10:53:30AM +0300, Dan Carpenter wrote:
> The problem here is:
> 
> 	ioffset = offset & ~(rounding - 1);
> 
> "offset" and "ioffset" are type xfs_off_t (__s64) and "rounding" is
> unsigned int.  The "offset & ~(rounding - 1)" clears the high 32 bits
> and which is unintentional.
> 
> This is a static checker fix so I'm not sure how much difference this
> makes in real life.

It is a real problem, but one that is masked by the way we do range
flushing right now.

As it is, the static checker missed the:

	rounding = max_t(uint, ....);

The line before the above usage. I posted a patch to fix this this
2 weeks ago here:

http://oss.sgi.com/pipermail/xfs/2013-May/025986.html

But thanks for the independent confirmation of the problem, Dan. ;)

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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  reply	other threads:[~2013-05-16 23:03 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-16  7:53 [patch] xfs: bug widening binary "not" operation Dan Carpenter
2013-05-16  7:53 ` Dan Carpenter
2013-05-16 23:03 ` Dave Chinner [this message]
2013-05-16 23:03   ` Dave Chinner
2013-05-17  6:31   ` Dan Carpenter
2013-05-17  6:31     ` Dan Carpenter
2013-05-17 10:19     ` Dave Chinner
2013-05-17 10:19       ` Dave Chinner

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