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    SubjectRe: [PATCH] iommu/amd: Check if domain is NULL before dereference it
    On 08/24/17 at 03:32pm, Dan Carpenter wrote:
    > Take a look at this code for example. But all the places which call
    > get_domain() are the same:
    >
    > drivers/iommu/amd_iommu.c
    > 2648 page = virt_to_page(virt_addr);
    > 2649 size = PAGE_ALIGN(size);
    > 2650
    > 2651 domain = get_domain(dev);
    > ^^^^^^^^^^^^^^
    > imagined get_domain() returns NULL.
    >
    > 2652 if (IS_ERR(domain))
    > 2653 goto free_mem;
    > 2654
    > 2655 dma_dom = to_dma_ops_domain(domain);
    > ^^^^^^^^^^^^^^^^^^^^^^^^^
    > This will Oops.

    I see, it's a problem. Thanks for telling!

    How about below change? But I am not very sure which errno should be
    picked, seems the latter one, EBUSY is better since it has passed the
    check_device() checking.

    diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
    index 16f1e6af00b0..2d7d04472555 100644
    --- a/drivers/iommu/amd_iommu.c
    +++ b/drivers/iommu/amd_iommu.c
    @@ -2262,6 +2262,9 @@ static struct protection_domain *get_domain(struct device *dev)
    domain = to_pdomain(io_domain);
    attach_device(dev, domain);
    }
    + if (domain == NULL)
    + return ERR_PTR(-EBUSY);
    +
    if (!dma_ops_domain(domain))
    return ERR_PTR(-EBUSY);

    --
    2.5.5
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