[RFC PATCH v2] iommu: Add sanity check to iommu_sva_bind_device()

[Jerry Snitselaar <jsnitsel@redhat.com>]

iommu_sva_bind_device() should only be called if
iommu_dev_enable_feature() succeeded. There has been one case already
where that hasn't been the case, which resulted in a null pointer
deref in dev_iommu_ops(). To avoid that happening in the future if
another driver makes that mistake, sanity check dev->iommu and
dev->iommu->iommu_dev prior to calling dev_iommu_ops().

Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
---
v2: Fix summary, and typo in dev_warn()

drivers/iommu/iommu.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 4893c2429ca5..c745e935f26a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2746,7 +2746,15 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
 {
 	struct iommu_group *group;
 	struct iommu_sva *handle = ERR_PTR(-EINVAL);
-	const struct iommu_ops *ops = dev_iommu_ops(dev);
+	const struct iommu_ops *ops;
+
+	if (!dev->iommu || !dev->iommu->iommu_dev) {
+		dev_warn(dev, "%s called without checking success of iommu_dev_enable_feature?\n",
+			__func__);
+		return ERR_PTR(-ENODEV);
+	}
+
+	ops = dev_iommu_ops(dev);
 
 	if (!ops->sva_bind)
 		return ERR_PTR(-ENODEV);
-- 
2.37.2