iommufd: Do not allow _iommufd_object_alloc_ucmd if abort op is set

An abort op was introduced to allow its caller to invoke it within a lock
in the caller's function. On the other hand, _iommufd_object_alloc_ucmd()
would invoke the abort op in iommufd_object_abort_and_destroy() that must
be outside the caller's lock. So, these two cannot work together.

Add a validation in the _iommufd_object_alloc_ucmd(). Pick -EOPNOTSUPP to
reject the function call, indicating that the object allocator is buggy.

Link: https://patch.msgid.link/r/[email protected]
Suggested-by: Xu Yilun <[email protected]>
Signed-off-by: Nicolin Chen <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Reviewed-by: Xu Yilun <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: nicolinc

drivers/iommu/iommufd/main.c

@@ -71,6 +71,15 @@ struct iommufd_object *_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd,
 	if (WARN_ON(ucmd->new_obj))
 		return ERR_PTR(-EBUSY);
 
+	/*
+	 * An abort op means that its caller needs to invoke it within a lock in
+	 * the caller. So it doesn't work with _iommufd_object_alloc_ucmd() that
+	 * will invoke the abort op in iommufd_object_abort_and_destroy(), which
+	 * must be outside the caller's lock.
+	 */
+	if (WARN_ON(iommufd_object_ops[type].abort))
+		return ERR_PTR(-EOPNOTSUPP);
+
 	new_obj = _iommufd_object_alloc(ucmd->ictx, size, type);
 	if (IS_ERR(new_obj))
 		return new_obj;