e946f8e3e6
Several functions obtain the group reference and then release it before returning. This gives the impression that the refcount is protecting something for the duration of the function. In truth all of these functions are called in places that know a device driver is probed to the device and our locking rules already require that dev->iommu_group cannot change while a driver is attached to the struct device. If this was not the case then this code is already at risk of triggering UAF as it is racy if the dev->iommu_group is concurrently going to NULL/free. refcount debugging will throw a WARN if kobject_get() is called on a 0 refcount object to highlight the bug. Remove the confusing refcounting and leave behind a comment about the restriction. Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Link: https://lore.kernel.org/r/1-v1-c869a95191f2+5e8-iommu_single_grp_jgg@nvidia.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.