From b7c21bc56fbedf4a61b628c6b11e0d7048746cc1 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 20 Apr 2018 15:20:26 -0700 Subject: [PATCH] x86/pti: Disallow global kernel text with RANDSTRUCT commit 26d35ca6c3776784f8156e1d6f80cc60d9a2a915 RANDSTRUCT derives its hardening benefits from the attacker's lack of knowledge about the layout of kernel data structures. Keep the kernel image non-global in cases where RANDSTRUCT is in use to help keep the layout a secret. Fixes: 8c06c7740 (x86/pti: Leave kernel text global for !PCID) Reported-by: Kees Cook Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Andrea Arcangeli Cc: Juergen Gross Cc: Josh Poimboeuf Cc: Greg Kroah-Hartman Cc: Peter Zijlstra Cc: David Woodhouse Cc: Hugh Dickins Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Borislav Petkov Cc: Andy Lutomirski Cc: Nadav Amit Cc: Dan Williams Cc: Arjan van de Ven Cc: Vlastimil Babka Link: https://lkml.kernel.org/r/20180420222026.D0B4AAC9@viggo.jf.intel.com --- arch/x86/mm/pti.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index ae3eb4f5d53b..4d418e705878 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -421,6 +421,16 @@ static inline bool pti_kernel_image_global_ok(void) if (boot_cpu_has(X86_FEATURE_K8)) return false; + /* + * RANDSTRUCT derives its hardening benefits from the + * attacker's lack of knowledge about the layout of kernel + * data structures. Keep the kernel image non-global in + * cases where RANDSTRUCT is in use to help keep the layout a + * secret. + */ + if (IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT)) + return false; + return true; } -- 2.30.2