Re: [Xen-devel] Xen security advisory CVE-2011-1898 - VT-d (PCI passthrough) MSI

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Wed, 2011-05-18 at 11:03 +0100, Keir Fraser wrote:
> On 18/05/2011 09:53, "Ian Campbell" <Ian.Campbell@xxxxxxxxxxxxx> wrote:
> 
> > On Mon, 2011-05-16 at 22:34 +0100, Cihula, Joseph wrote:
> >>> -    if ( iommu_intremap )
> >>> -    {
> >>> +
> >> 
> >> Unless I'm misreading it, this will prevent users from specifying
> >> "no-intremap" to disable the use of IR.
> > 
> > That wasn't my intention.
> > 
> >> Why would you keep the 'if ( iommu_intremap )' on the previous code
> >> block but remove it here?
> > 
> > To be honest this change was a little bit unrelated, which was naughty
> > of me. I saw:
> > if ( iommu_intremap ) {
> > THING A
> > }
> > if ( iommu_intremap ) {
> > THING B
> > }
> > and changed it to
> > if (iommu_intremap ) {
> > THING A
> > THING B
> > }
> > 
> > Is there some subtlety to this code path that I've missed?
> 
> 'THING A' conditionally clears iommu_intremap.

Right, but in this patch I was switching those to panic()s, so maybe not
such an unrelated change after all.

Anyway, I don't think this patch is going to fly so it doesn't really
matter.

Ian.



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