From 5280fab9bb19e94b1ea5046dc1360f121ec64c0f Mon Sep 17 00:00:00 2001 From: Rudolf Marek Date: Tue, 28 Nov 2017 22:01:06 +0100 Subject: [PATCH 122/242] x86: Make X86_BUG_FXSAVE_LEAK detectable in CPUID on AMD MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit CVE-2017-5754 [ Note, this is a Git cherry-pick of the following commit: 2b67799bdf25 ("x86: Make X86_BUG_FXSAVE_LEAK detectable in CPUID on AMD") ... for easier x86 PTI code testing and back-porting. ] The latest AMD AMD64 Architecture Programmer's Manual adds a CPUID feature XSaveErPtr (CPUID_Fn80000008_EBX[2]). If this feature is set, the FXSAVE, XSAVE, FXSAVEOPT, XSAVEC, XSAVES / FXRSTOR, XRSTOR, XRSTORS always save/restore error pointers, thus making the X86_BUG_FXSAVE_LEAK workaround obsolete on such CPUs. Signed-Off-By: Rudolf Marek Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Tested-by: Borislav Petkov Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/bdcebe90-62c5-1f05-083c-eba7f08b2540@assembler.cz Signed-off-by: Ingo Molnar (cherry picked from commit f2dbad36c55e5d3a91dccbde6e8cae345fe5632f) Signed-off-by: Andy Whitcroft Signed-off-by: Kleber Sacilotto de Souza (cherry picked from commit 281b622113c66ba2de9b7725e1d232ea3c282114) Signed-off-by: Fabian Grünbichler --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/cpu/amd.c | 7 +++++-- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 0ea630bb3e74..d57a174ec97c 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -265,6 +265,7 @@ /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */ #define X86_FEATURE_CLZERO (13*32+ 0) /* CLZERO instruction */ #define X86_FEATURE_IRPERF (13*32+ 1) /* Instructions Retired Count */ +#define X86_FEATURE_XSAVEERPTR (13*32+ 2) /* Always save/restore FP error pointers */ /* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */ #define X86_FEATURE_DTHERM (14*32+ 0) /* Digital Thermal Sensor */ diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 3b9e220621f8..2a5328cc03a6 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -760,8 +760,11 @@ static void init_amd(struct cpuinfo_x86 *c) case 0x15: init_amd_bd(c); break; } - /* Enable workaround for FXSAVE leak */ - if (c->x86 >= 6) + /* + * Enable workaround for FXSAVE leak on CPUs + * without a XSaveErPtr feature + */ + if ((c->x86 >= 6) && (!cpu_has(c, X86_FEATURE_XSAVEERPTR))) set_cpu_bug(c, X86_BUG_FXSAVE_LEAK); cpu_detect_cache_sizes(c); -- 2.14.2