Re: [syzbot] test uaf in iommufd_vfio_ioas

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Subject: test uaf in iommufd_vfio_ioas
Author: lizhi.xu@xxxxxxxxxxxxx

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2af9b20dbb39

diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index e71523cbd0de..e89c90784536 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -159,7 +159,8 @@ static struct iommufd_object *iommufd_object_remove(struct iommufd_ctx *ictx,
 	}
 
 	xas_store(&xas, NULL);
-	if (ictx->vfio_ioas == container_of(obj, struct iommufd_ioas, obj))
+	__xa_erase(&ictx->objects, obj->id);
+	if (ictx->vfio_ioas && &ictx->vfio_ioas->obj == obj)
 		ictx->vfio_ioas = NULL;
 
 out_xa: