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Date: Wed, 17 Feb 2016 14:41:11 -0800
From: Kees Cook <keescook@...omium.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
David Brown <david.brown@...aro.org>,
Andy Lutomirski <luto@...capital.net>,
"H. Peter Anvin" <hpa@...or.com>,
Michael Ellerman <mpe@...erman.id.au>,
Mathias Krause <minipli@...glemail.com>,
Thomas Gleixner <tglx@...utronix.de>,
x86@...nel.org,
Arnd Bergmann <arnd@...db.de>,
PaX Team <pageexec@...email.hu>,
Emese Revfy <re.emese@...il.com>,
kernel-hardening@...ts.openwall.com,
linux-kernel@...r.kernel.org,
linux-arch <linux-arch@...r.kernel.org>
Subject: [PATCH v5 0/7] 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 and arm 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.
-Kees
v5:
- rebased on linux-next (strtobool in -next, x86 vdso merge fixup)
- added ARM vDSO patch, david.brown
v4:
- adjust documentation for strtobool, andy.shevchenko
v3:
- 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
v2:
- renamed __read_only to __ro_after_init
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