On Wed, 2015-03-11 at 09:57 +1100, Alexey Kardashevskiy wrote:
> On 03/11/2015 06:56 AM, Alex Williamson wrote:
> > On Tue, 2015-03-10 at 01:06 +1100, Alexey Kardashevskiy wrote:
> >> This checks that the TCE table page size is not bigger that the size of
> >> a page we just pinned and going to put its physical address to the table.
> >>
> >> Otherwise the hardware gets unwanted access to physical memory between
> >> the end of the actual page and the end of the aligned up TCE page.
> >>
> >> Since compound_order() and compound_head() work correctly on non-huge
> >> pages, there is no need for additional check whether the page is huge.
> >>
> >> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> >> ---
> >> Changes:
> >> v4:
> >> * s/tce_check_page_size/tce_page_is_contained/
> >> ---
> >> drivers/vfio/vfio_iommu_spapr_tce.c | 22 ++++++++++++++++++++++
> >> 1 file changed, 22 insertions(+)
> >>
> >> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> >> index 756831f..91e7599 100644
> >> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> >> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> >> @@ -49,6 +49,22 @@ struct tce_container {
> >> bool enabled;
> >> };
> >>
> >> +static bool tce_page_is_contained(struct page *page, unsigned page_shift)
> >> +{
> >> + unsigned shift;
> >> +
> >> + /*
> >> + * Check that the TCE table granularity is not bigger than the size of
> >> + * a page we just found. Otherwise the hardware can get access to
> >> + * a bigger memory chunk that it should.
> >> + */
> >> + shift = PAGE_SHIFT + compound_order(compound_head(page));
> >> + if (shift >= page_shift)
> >> + return true;
> >> +
> >> + return false;
> >
> > nit, simplified:
> >
> > return (PAGE_SHIFT + compound_order(compound_head(page) >= page_shift);
>
> This won't be "bool" though.
Yes, it will.
> This will (I'll do this)
>
> shift = PAGE_SHIFT + compound_order(compound_head(page));
> return (shift >= page_shift);
>
>
>
>
> >
> >> +}
> >> +
> >> static int tce_iommu_enable(struct tce_container *container)
> >> {
> >> int ret = 0;
> >> @@ -197,6 +213,12 @@ static long tce_iommu_build(struct tce_container *container,
> >> ret = -EFAULT;
> >> break;
> >> }
> >> +
> >> + if (!tce_page_is_contained(page, tbl->it_page_shift)) {
> >> + ret = -EPERM;
> >> + break;
> >> + }
> >> +
> >> hva = (unsigned long) page_address(page) +
> >> (tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK);
> >>
> >
> >
> >
>
>
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