x86/mm/pti: Add Kconfig

CVE-2017-5754

Finally allow CONFIG_PAGE_TABLE_ISOLATION to be enabled.

PARAVIRT generally requires that the kernel not manage its own page tables.
It also means that the hypervisor and kernel must agree wholeheartedly
about what format the page tables are in and what they contain.
PAGE_TABLE_ISOLATION, unfortunately, changes the rules and they
can not be used together.

I've seen conflicting feedback from maintainers lately about whether they
want the Kconfig magic to go first or last in a patch series.  It's going
last here because the partially-applied series leads to kernels that can
not boot in a bunch of cases.  I did a run through the entire series with
CONFIG_PAGE_TABLE_ISOLATION=y to look for build errors, though.

[ tglx: Removed SMP and !PARAVIRT dependencies as they not longer exist ]

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 385ce0ea4c078517fa51c261882c4e72fba53005)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/security/Kconfig b/security/Kconfig
index 305b496ff6a3d1a87a11483a4d4b049c33012f04..91cb8f611a0d1861e99fe12e69879291f8e1e4a7 100644 (file)
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -96,6 +96,16 @@ config SECURITY_NETWORK
          implement socket and networking access controls.
          If you are unsure how to answer this question, answer N.
 
+config PAGE_TABLE_ISOLATION
+       bool "Remove the kernel mapping in user mode"
+       depends on X86_64 && !UML
+       help
+         This feature reduces the number of hardware side channels by
+         ensuring that the majority of kernel addresses are not mapped
+         into userspace.
+
+         See Documentation/x86/pagetable-isolation.txt for more details.
+
 config SECURITY_INFINIBAND
        bool "Infiniband Security Hooks"
        depends on SECURITY && INFINIBAND