diff options
| author | Kees Cook <keescook@chromium.org> | 2013-04-10 12:24:22 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2013-04-11 13:53:19 -0700 |
| commit | 4eefbe792baedb474e256d35370849992fcf1c79 (patch) | |
| tree | 03a95dab4a014a7f36133f9660ca180b01df62d4 /arch/x86/kernel/traps.c | |
| parent | 31880c37c11e28cb81c70757e38392b42e695dc6 (diff) | |
x86: Use a read-only IDT alias on all CPUs
Make a copy of the IDT (as seen via the "sidt" instruction) read-only.
This primarily removes the IDT from being a target for arbitrary memory
write attacks, and has the added benefit of also not leaking the kernel
base offset, if it has been relocated.
We already did this on vendor == Intel and family == 5 because of the
F0 0F bug -- regardless of if a particular CPU had the F0 0F bug or
not. Since the workaround was so cheap, there simply was no reason to
be very specific. This patch extends the readonly alias to all CPUs,
but does not activate the #PF to #UD conversion code needed to deliver
the proper exception in the F0 0F case except on Intel family 5
processors.
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/20130410192422.GA17344@www.outflux.net
Cc: Eric Northup <digitaleric@google.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/traps.c')
| -rw-r--r-- | arch/x86/kernel/traps.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 68bda7a84159..10e24462c058 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -56,6 +56,7 @@ #include <asm/fpu-internal.h> #include <asm/mce.h> #include <asm/context_tracking.h> +#include <asm/fixmap.h> #include <asm/mach_traps.h> @@ -753,6 +754,14 @@ 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(); |