Re: [PATCH] mptsas: fix undefined behaviour of a shift of an int by more than 31 places

[Hannes Reinecke]

On 5/8/19 4:24 PM, James Bottomley wrote:
> On Wed, 2019-05-08 at 14:07 +0100, Colin Ian King wrote:
> > On 05/05/2019 04:34, James Bottomley wrote:
> > > On Sat, 2019-05-04 at 17:40 +0100, Colin King wrote:
> > > > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > > >
> > > > Currently the shift of int value 1 by more than 31 places can
> > > > result in undefined behaviour. Fix this by making the 1 a ULL
> > > > value before the shift operation.
> > >
> > > Fusion SAS is pretty ancient.  I thought the largest one ever
> > > produced had four phys, so how did you produce the overflow?
> >
> > This was an issue found by static analysis with Coverity; so I guess
> > won't happen in the wild, in which case the patch could be ignored.
>
> The point I was more making is that if we thought this could ever
> happen in practice, we'd need more error handling than simply this:
> we'd be setting the phy_bitmap to zero which would be every bit as bad
> as some random illegal value.
Thing is, mptsas is used as the default emulation in VMWare, and that 
does allow you to do some pretty weird configurations (I've found myself 
fixing a bug with SATA hotplug on mptsas once ...).
So I wouldn't discard this issue out of hand.

Cheers,

Hannes
--
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@xxxxxxx                              +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 NÃrnberg
GF: Felix ImendÃrffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG NÃrnberg)