iommufd: Fix locking around hwpt allocation

Due to the auto_domains mechanism the ioas->mutex must be held until
the hwpt is completely setup by iommufd_object_abort_and_destroy() or
iommufd_object_finalize().

This prevents a concurrent iommufd_device_auto_get_domain() from seeing
an incompletely initialized object through the ioas->hwpt_list.

To make this more consistent move the unlock until after finalize.

Fixes: e8d57210035b ("iommufd: Add kAPI toward external drivers for physical devices")
Link: https://lore.kernel.org/r/11-v8-6659224517ea+532-iommufd_alloc_jgg@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 08bba99f2fb01e3de2a201bb588e4981a8a9e476..9b9244c5b0ce45b5c2269c82bb44a7e55c0239da 100644 (file)
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -441,8 +441,8 @@ static int iommufd_device_auto_get_domain(struct iommufd_device *idev,
        hwpt->auto_domain = true;
        *pt_id = hwpt->obj.id;
 
-       mutex_unlock(&ioas->mutex);
        iommufd_object_finalize(idev->ictx, &hwpt->obj);
+       mutex_unlock(&ioas->mutex);
        return 0;
 out_unlock:
        mutex_unlock(&ioas->mutex);