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The kvmgt code keeps a pointer to the struct kvm associated with the device, but doesn't actually hold a reference to it. If we do unclean shutdown testing (ie. killing the user process), then we can see the kvm association to the device unset, which causes kvmgt to trigger a device release via a work queue. Naturally we cannot guarantee that the cached struct kvm pointer is still valid at this point without holding a reference. The observed failure in this case is a stuck cpu trying to acquire the spinlock from the invalid reference, but other failure modes are clearly possible. Hold a reference to avoid this. Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Cc: stable@vger.kernel.org #v4.10 Cc: Jike Song <jike.song@intel.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: Zhi Wang <zhi.a.wang@intel.com> Reviewed-by: Jike Song <jike.song@intel.com> Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.