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When ashmem file is mmapped, the resulting vma->vm_file points to the backing shmem file with the generic fops that do not check ashmem permissions like fops of ashmem do. If an mremap is done on the ashmem region, then the permission checks will be skipped. Fix that by disallowing mapping operation on the backing shmem file. Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Suren Baghdasaryan <surenb@google.com> Cc: stable <stable@vger.kernel.org> # 4.4,4.9,4.14,4.18,5.4 Signed-off-by: Todd Kjos <tkjos@google.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Link: https://lore.kernel.org/r/20200127235616.48920-1-tkjos@google.com 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.