[PATCH] x86/xen: add physically contiguous check to xen_destroy_contiguous_region

[Joe Jin <joe.jin@oracle.com>]

xen_destroy_contiguous_region() used to exchange physically
contiguous memory with hypervisor, but it does not verify
that the memory is physically contiguous or no, passing
non-contiguous memory to xen_destroy_contiguous_region()
will lead kernel panic.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
---
 arch/x86/xen/mmu_pv.c     | 3 +++
 drivers/xen/swiotlb-xen.c | 3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 70ea598a37d2..c2f081f8ebe3 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -2649,6 +2649,9 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
 	if (unlikely(order > MAX_CONTIG_ORDER))
 		return;
 
+	if (range_straddles_page_boundary(pstart, PAGE_SIZE << order))
+		return;
+
 	vstart = (unsigned long)phys_to_virt(pstart);
 	memset((void *) vstart, 0, PAGE_SIZE << order);
 
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index f5c1af4ce9ab..432eeae02d7d 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -357,8 +357,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
 	/* Convert the size to actually allocated. */
 	size = 1UL << (order + XEN_PAGE_SHIFT);
 
-	if (((dev_addr + size - 1 <= dma_mask)) ||
-	    range_straddles_page_boundary(phys, size))
+	if (dev_addr + size - 1 <= dma_mask)
 		xen_destroy_contiguous_region(phys, order);
 
 	xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
-- 
2.17.1 (Apple Git-112)