Messages in this thread | | | Date | Wed, 9 Sep 2015 16:37:18 -0700 | From | Brian Norris <> | Subject | Re: [PATCH] mtd: blktrans: fix integer overflow |
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On Sat, Sep 05, 2015 at 09:42:27PM +0800, Peng Fan wrote: > On Wed, Sep 02, 2015 at 10:02:49AM -0700, Brian Norris wrote: > > One possibility, since you only point to a single computation that > > overflows, is to just fix the overflow locally. It's not like the 'size' > > (which represents number of sectors) is actually ever overflowing a > > 32-bit integer. It's just the multiplication that overflows. So you > > could cast to 64-bit arithmetic just for the multiplication. e.g.: > > > > set_capcity(gd, ((u64)new->size * tr->blksize) >> 9); > > Yeah. It is the multiplication overflowing a 32-bit interger. My frist > implementation is this way, using u64 to do type cast. But I guess one > day the number of sectors can be larger than UINT_MAX, so I change it > to 'unsigned long long' from 'unsigned long', which is > not the right way, thanks for correcting me. > > > > Or some other creative solution. > > I think this should be a bug fix. If you need a quick fix, I can send > out the simple patch that just do (u64) cast. If not, I can take some > time to "fix all the blktrans users".
I think since you've identified (and tested) a fix, we might as well include it. So I suppose the cast approach. The larger change would be more invasive and may take a while.
> > > > Then, we don't have to address this problem till we start seeing 2TB > > MTDs!
Brian
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