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    Subject[PATCH 3.2 047/152] iommu/vt-d: Fix an off-by-one bug in __domain_mapping()
    3.2.67-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jiang Liu <jiang.liu@linux.intel.com>

    commit cc4f14aa170d895c9a43bdb56f62070c8a6da908 upstream.

    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>
    Acked-By: David Woodhouse <David.Woodhouse@intel.com>
    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    [bwh: Backported to 3.2: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/iommu/intel-iommu.c | 8 +++-----
    1 file changed, 3 insertions(+), 5 deletions(-)

    --- a/drivers/iommu/intel-iommu.c
    +++ b/drivers/iommu/intel-iommu.c
    @@ -1763,7 +1763,7 @@ 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;

    @@ -1774,10 +1774,8 @@ 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;
    }



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