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Date: Tue, 24 Nov 2015 13:38:32 -0800
From: Kees Cook <>
Cc: Kees Cook <>, Andy Lutomirski <>,
        Ingo Molnar <>, Thomas Gleixner <>,
        "H. Peter Anvin" <>,,
        Arnd Bergmann <>, Michael Ellerman <>,,
Subject: [PATCH 0/2] introduce post-init read-only memory

One of the easiest ways to protect the kernel from attack is to reduce
the internal attack surface exposed when a "write" flaw is available. By
making as much of the kernel read-only as possible, we reduce the
attack surface.

Many things are written to only during __init, and never changed
again. These cannot be made "const" since the compiler will do the wrong
thing (we do actually need to write to them). Instead, move these items
into a memory region that will be made read-only during mark_rodata_ro()
which happens after all kernel __init code has finished.

This introduces __read_only as a way to mark such memory, and uses it on
the x86 vDSO to kill an extant kernel exploitation method.


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