c3d06f6067
commit f55aaf63bde0d0336c3823bb3713bd4a464abbcf upstream. The postclose handler can run after the device has been removed (or the driver has been unbound) since userspace clients are free to hold the file open as long as they want. Because the device removal callback frees the entire nouveau_drm structure, any reference to it in the postclose handler will result in a use-after-free. To reproduce this, one must simply open the device file, unbind the driver (or physically remove the device), and then close the device file. This was found and can be reproduced easily with the IGT core_hotunplug tests. To avoid this, all clients are cleaned up in the device finalization rather than deferring it to the postclose handler, and the postclose handler is protected by a critical section which ensures the drm_dev_unplug() and the postclose handler won't race. This is not an ideal fix, since as I understand the proposed plan for the kernel<->userspace interface for hotplug support, destroying the client before the file is closed will cause problems. However, I believe to properly fix this issue, the lifetime of the nouveau_drm structure needs to be extended to match the drm_device, and this proved to be a rather invasive change. Thus, I've broken this out so the fix can be easily backported. This fixes with the two previous commits CVE-2020-27820 (Karol). Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Jeremy Cline <jcline@redhat.com> Reviewed-by: Lyude Paul <lyude@redhat.com> Reviewed-by: Ben Skeggs <bskeggs@redhat.com> Tested-by: Karol Herbst <kherbst@redhat.com> Signed-off-by: Karol Herbst <kherbst@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201125202648.5220-4-jcline@redhat.com Link: https://gitlab.freedesktop.org/drm/nouveau/-/merge_requests/14 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.