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cd5297b085
Nothing checks userptr.ro except this call to pup_fast, which means there's nothing actually preventing userspace from writing to this. Which means you can just read-only mmap any file you want, userptr it and then write to it with the gpu. Not good. The right way to handle this is FOLL_WRITE | FOLL_FORCE, which will break any COW mappings and update tracking for MAY_WRITE mappings so there's no exploit and the vm isn't confused about what's going on. For any legit use case there's no difference from what userspace can observe and do. Reviewed-by: Lucas Stach <l.stach@pengutronix.de> Cc: stable@vger.kernel.org Cc: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Cc: Lucas Stach <l.stach@pengutronix.de> Cc: Russell King <linux+etnaviv@armlinux.org.uk> Cc: Christian Gmeiner <christian.gmeiner@gmail.com> Cc: etnaviv@lists.freedesktop.org Link: https://patchwork.freedesktop.org/patch/msgid/20210301095254.1946084-1-daniel.vetter@ffwll.ch
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.