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    Subject[PATCH AUTOSEL 4.14 010/109] powerpc/iommu: Avoid derefence before pointer check
    Date
    From: Breno Leitao <leitao@debian.org>

    [ Upstream commit 984ecdd68de0fa1f63ce205d6c19ef5a7bc67b40 ]

    The tbl pointer is being derefenced by IOMMU_PAGE_SIZE prior the check
    if it is not NULL.

    Just moving the dereference code to after the check, where there will
    be guarantee that 'tbl' will not be NULL.

    Signed-off-by: Breno Leitao <leitao@debian.org>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kernel/iommu.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
    index af7a20dc6e093..80b6caaa9b92e 100644
    --- a/arch/powerpc/kernel/iommu.c
    +++ b/arch/powerpc/kernel/iommu.c
    @@ -785,9 +785,9 @@ dma_addr_t iommu_map_page(struct device *dev, struct iommu_table *tbl,

    vaddr = page_address(page) + offset;
    uaddr = (unsigned long)vaddr;
    - npages = iommu_num_pages(uaddr, size, IOMMU_PAGE_SIZE(tbl));

    if (tbl) {
    + npages = iommu_num_pages(uaddr, size, IOMMU_PAGE_SIZE(tbl));
    align = 0;
    if (tbl->it_page_shift < PAGE_SHIFT && size >= PAGE_SIZE &&
    ((unsigned long)vaddr & ~PAGE_MASK) == 0)
    --
    2.20.1
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