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    Subject[PATCH 5.4 027/214] iommu/iova: Dont BUG on invalid PFNs
    Date
    From: Robin Murphy <robin.murphy@arm.com>

    [ Upstream commit d3e3d2be688b4b5864538de61e750721a311e4fc ]

    Unlike the other instances which represent a complete loss of
    consistency within the rcache mechanism itself, or a fundamental
    and obvious misconfiguration by an IOMMU driver, the BUG_ON() in
    iova_magazine_free_pfns() can be provoked at more or less any time
    in a "spooky action-at-a-distance" manner by any old device driver
    passing nonsense to dma_unmap_*() which then propagates through to
    queue_iova().

    Not only is this well outside the IOVA layer's control, it's also
    nowhere near fatal enough to justify panicking anyway - all that
    really achieves is to make debugging the offending driver more
    difficult. Let's simply WARN and otherwise ignore bogus PFNs.

    Reported-by: Prakash Gupta <guptap@codeaurora.org>
    Signed-off-by: Robin Murphy <robin.murphy@arm.com>
    Reviewed-by: Prakash Gupta <guptap@codeaurora.org>
    Link: https://lore.kernel.org/r/acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com
    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/iommu/iova.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
    index 0e6a9536eca62..612cbf668adf8 100644
    --- a/drivers/iommu/iova.c
    +++ b/drivers/iommu/iova.c
    @@ -811,7 +811,9 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
    for (i = 0 ; i < mag->size; ++i) {
    struct iova *iova = private_find_iova(iovad, mag->pfns[i]);

    - BUG_ON(!iova);
    + if (WARN_ON(!iova))
    + continue;
    +
    private_free_iova(iovad, iova);
    }

    --
    2.25.1


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