From c74ba8b3480da6ddaea17df2263ec09b869ac496 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 17 Feb 2016 14:41:15 -0800 Subject: arch: 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 adds some documentation about the existing __read_mostly marking. This improves the security of the Linux kernel by marking formerly read-write memory regions as read-only on a fully booted up system. Based on work by PaX Team and Brad Spengler. Signed-off-by: Kees Cook Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Brad Spengler Cc: Brian Gerst Cc: David Brown Cc: Denys Vlasenko Cc: Emese Revfy Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Mathias Krause Cc: Michael Ellerman Cc: PaX Team Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: kernel-hardening@lists.openwall.com Cc: linux-arch Link: http://lkml.kernel.org/r/1455748879-21872-5-git-send-email-keescook@chromium.org Signed-off-by: Ingo Molnar --- arch/parisc/include/asm/cache.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/parisc/include/asm') diff --git a/arch/parisc/include/asm/cache.h b/arch/parisc/include/asm/cache.h index 3d0e17b..df0f52b 100644 --- a/arch/parisc/include/asm/cache.h +++ b/arch/parisc/include/asm/cache.h @@ -22,6 +22,9 @@ #define __read_mostly __attribute__((__section__(".data..read_mostly"))) +/* Read-only memory is marked before mark_rodata_ro() is called. */ +#define __ro_after_init __read_mostly + void parisc_cache_init(void); /* initializes cache-flushing */ void disable_sr_hashing_asm(int); /* low level support for above */ void disable_sr_hashing(void); /* turns off space register hashing */ -- cgit v1.1