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. 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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