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bd49e16e33
With vsyscall emulation on, a readable vsyscall page is still exposed that contains syscall instructions that validly implement the vsyscalls. This is required because certain dynamic binary instrumentation tools attempt to read the call targets of call instructions in the instrumented code. If the instrumented code uses vsyscalls, then the vsyscall page needs to contain readable code. Unfortunately, leaving readable memory at a deterministic address can be used to help various ASLR bypasses, so some hardening value can be gained by disallowing vsyscall reads. Given how rarely the vsyscall page needs to be readable, add a mechanism to make the vsyscall page be execute only. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Kernel Hardening <kernel-hardening@lists.openwall.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/d17655777c21bc09a7af1bbcf74e6f2b69a51152.1561610354.git.luto@kernel.org |
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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.