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Date: Tue, 19 Jan 2016 10:08:34 -0800
From: Kees Cook <>
To: Ingo Molnar <>
Cc: Kees Cook <>,
	Andy Lutomirski <>,
	"H. Peter Anvin" <>,
	Michael Ellerman <>,
	Mathias Krause <>,
	Thomas Gleixner <>,,
	Arnd Bergmann <>,
	PaX Team <>,
	Emese Revfy <>,,,
	linux-arch <>
Subject: [PATCH v4 0/8] 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 __ro_after_init as a way to mark such memory, and uses
it on the x86 vDSO to kill an extant kernel exploitation method. Also
adds a new kernel parameter to help debug future use and adds an lkdtm
test to check the results.


- rebased
- conslidated mark_rodata_ro()
- make CONFIG_DEBUG_RODATA always enabled on x86, mingo
- enhanced strtobool and potential callers to use "on"/"off"
- use strtobool for rodata= param, gregkh
- renamed __read_only to __ro_after_init

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