iommu/vt-d: fix memory leakage caused by commit ea8ea46

Commit ea8ea46 "iommu/vt-d: Clean up and fix page table clear/free
behaviour" introduces possible leakage of DMA page tables due to:
        for (pte = page_address(pg); !first_pte_in_page(pte); pte++) {
                if (dma_pte_present(pte) && !dma_pte_superpage(pte))
                        freelist = dma_pte_list_pagetables(domain, level - 1,
                                                           pte, freelist);
        }

For the first pte in a page, first_pte_in_page(pte) will always be true,
thus dma_pte_list_pagetables() will never be called and leak DMA page
tables if level is bigger than 1.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 69fa7da5e48b..13dc2318e17a 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1009,11 +1009,13 @@ static struct page *dma_pte_list_pagetables(struct dmar_domain *domain,
         if (level == 1)
                 return freelist;
 
-        for (pte = page_address(pg); !first_pte_in_page(pte); pte++) {
+        pte = page_address(pg);
+        do {
                 if (dma_pte_present(pte) && !dma_pte_superpage(pte))
                         freelist = dma_pte_list_pagetables(domain, level - 1,
                                                            pte, freelist);
-        }
+                pte++;
+        } while (!first_pte_in_page(pte));
 
         return freelist;
 }