Re: [patch] xfs: bug widening binary "not" operation

Dave Chinner
2013-05-16T23:03:14Z

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