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commit 6d67b0290b4b84c477e6a2fc6e005e174d3c7786 upstream. 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 ============ 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.