Re: [PATCH v3] iommu: Check dev->iommu in iommu_dev_xxx functions

[Robin Murphy]

On 2021-03-03 17:36, Shameer Kolothum wrote:

The device iommu probe/attach might have failed leaving dev->iommu
to NULL and device drivers may still invoke these functions resulting
in a crash in iommu vendor driver code.

Hence make sure we check that.

Reviewed-by: Robin Murphy <robin.mur...@arm.com>

Fixes: a3a195929d40 ("iommu: Add APIs for multiple domains per device")
Signed-off-by: Shameer Kolothum <shameerali.kolothum.th...@huawei.com>
---
v2 --> v3
  -Removed iommu_ops from struct dev_iommu.
v1 --> v2:
  -Added iommu_ops to struct dev_iommu based on the discussion with Robin.
  -Rebased against iommu-tree core branch.
---
  drivers/iommu/iommu.c | 24 +++++++++++++++---------
  1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d0b0a15dba84..e10cfa99057c 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2878,10 +2878,12 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);
   */
  int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features feat)
  {
-       const struct iommu_ops *ops = dev->bus->iommu_ops;
+       if (dev->iommu && dev->iommu->iommu_dev) {
+               const struct iommu_ops *ops = dev->iommu->iommu_dev->ops;

- if (ops && ops->dev_enable_feat)

-               return ops->dev_enable_feat(dev, feat);
+               if (ops->dev_enable_feat)
+                       return ops->dev_enable_feat(dev, feat);
+       }

return -ENODEV;

  }
@@ -2894,10 +2896,12 @@ EXPORT_SYMBOL_GPL(iommu_dev_enable_feature);
   */
  int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features 
feat)
  {
-       const struct iommu_ops *ops = dev->bus->iommu_ops;
+       if (dev->iommu && dev->iommu->iommu_dev) {
+               const struct iommu_ops *ops = dev->iommu->iommu_dev->ops;

- if (ops && ops->dev_disable_feat)

-               return ops->dev_disable_feat(dev, feat);
+               if (ops->dev_disable_feat)
+                       return ops->dev_disable_feat(dev, feat);
+       }

return -EBUSY;

  }
@@ -2905,10 +2909,12 @@ EXPORT_SYMBOL_GPL(iommu_dev_disable_feature);

bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features feat)

  {
-       const struct iommu_ops *ops = dev->bus->iommu_ops;
+       if (dev->iommu && dev->iommu->iommu_dev) {
+               const struct iommu_ops *ops = dev->iommu->iommu_dev->ops;

- if (ops && ops->dev_feat_enabled)

-               return ops->dev_feat_enabled(dev, feat);
+               if (ops->dev_feat_enabled)
+                       return ops->dev_feat_enabled(dev, feat);
+       }

return false;

  }