From: Jiang Liu <jiang.liu@linux.intel.com>
Date: Wed, 26 Nov 2014 09:42:10 +0800
Subject: iommu/vt-d: Fix an off-by-one bug in __domain_mapping()
Git-commit: cc4f14aa170d895c9a43bdb56f62070c8a6da908
Patch-mainline: v3.19-rc1
References: bsc#908825

There's an off-by-one bug in function __domain_mapping(), which may
trigger the BUG_ON(nr_pages < lvl_pages) when
	(nr_pages + 1) & superpage_mask == 0

The issue was introduced by commit 9051aa0268dc "intel-iommu: Combine
domain_pfn_mapping() and domain_sg_mapping()", which sets sg_res to
"nr_pages + 1" to avoid some of the 'sg_res==0' code paths.

It's safe to remove extra "+1" because sg_res is only used to calculate
page size now.

Reported-And-Tested-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: <stable@vger.kernel.org> # >= 3.0
Acked-By: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/pci/intel-iommu.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Index: linux-3.0-SLE11-SP3/drivers/pci/intel-iommu.c
===================================================================
--- linux-3.0-SLE11-SP3.orig/drivers/pci/intel-iommu.c
+++ linux-3.0-SLE11-SP3/drivers/pci/intel-iommu.c
@@ -1767,7 +1767,7 @@ static int __domain_mapping(struct dmar_
 	struct dma_pte *first_pte = NULL, *pte = NULL;
 	phys_addr_t uninitialized_var(pteval);
 	int addr_width = agaw_to_width(domain->agaw) - VTD_PAGE_SHIFT;
-	unsigned long sg_res;
+	unsigned long sg_res = 0;
 	unsigned int largepage_lvl = 0;
 	unsigned long lvl_pages = 0;
 
@@ -1778,10 +1778,8 @@ static int __domain_mapping(struct dmar_
 
 	prot &= DMA_PTE_READ | DMA_PTE_WRITE | DMA_PTE_SNP;
 
-	if (sg)
-		sg_res = 0;
-	else {
-		sg_res = nr_pages + 1;
+	if (!sg) {
+		sg_res = nr_pages;
 		pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | prot;
 	}
 
