Merge branch 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perparatory x86 kasrl changes from Ingo Molnar:
 "This contains changes from the ongoing KASLR work, by Kees Cook.

  The main changes are the use of a read-only IDT on x86 (which
  decouples the userspace visible virtual IDT address from the physical
  address), and a rework of ELF relocation support, in preparation of
  random, boot-time kernel image relocation."

* 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, relocs: Refactor the relocs tool to merge 32- and 64-bit ELF
  x86, relocs: Build separate 32/64-bit tools
  x86, relocs: Add 64-bit ELF support to relocs tool
  x86, relocs: Consolidate processing logic
  x86, relocs: Generalize ELF structure names
  x86: Use a read-only IDT alias on all CPUs

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index ff6d2271cbe2..772e2a846dec 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -56,6 +56,7 @@
 #include <asm/i387.h>
 #include <asm/fpu-internal.h>
 #include <asm/mce.h>
+#include <asm/fixmap.h>
 #include <asm/mach_traps.h>
 
 #ifdef CONFIG_X86_64
@@ -769,6 +770,14 @@ void __init trap_init(void)
 #endif
 
 	/*
+	 * Set the IDT descriptor to a fixed read-only location, so that the
+	 * "sidt" instruction will not leak the location of the kernel, and
+	 * to defend the IDT against arbitrary memory write vulnerabilities.
+	 * It will be reloaded in cpu_init() */
+	__set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);
+	idt_descr.address = fix_to_virt(FIX_RO_IDT);
+
+	/*
 	 * Should be a barrier for any external CPU state:
 	 */
 	cpu_init();