x86/cpufeatures: Add X86_BUG_CPU_INSECURE

Many x86 CPUs leak information to user space due to missing isolation of
user space and kernel space page tables. There are many well documented
ways to exploit that.

The upcoming software migitation of isolating the user and kernel space
page tables needs a misfeature flag so code can be made runtime
conditional.

Add the BUG bits which indicates that the CPU is affected and add a feature
bit which indicates that the software migitation is enabled.

Assume for now that _ALL_ x86 CPUs are affected by this. Exceptions can be
made later.

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: Dave Hansen <dave.hansen@linux.intel.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
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 800104c..d8ec834 100644 (file)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -201,7 +201,7 @@
 #define X86_FEATURE_HW_PSTATE          ( 7*32+ 8) /* AMD HW-PState */
 #define X86_FEATURE_PROC_FEEDBACK      ( 7*32+ 9) /* AMD ProcFeedbackInterface */
 #define X86_FEATURE_SME                        ( 7*32+10) /* AMD Secure Memory Encryption */
-
+#define X86_FEATURE_PTI                        ( 7*32+11) /* Kernel Page Table Isolation enabled */
 #define X86_FEATURE_INTEL_PPIN         ( 7*32+14) /* Intel Processor Inventory Number */
 #define X86_FEATURE_INTEL_PT           ( 7*32+15) /* Intel Processor Trace */
 #define X86_FEATURE_AVX512_4VNNIW      ( 7*32+16) /* AVX-512 Neural Network Instructions */
@@ -340,5 +340,6 @@
 #define X86_BUG_SWAPGS_FENCE           X86_BUG(11) /* SWAPGS without input dep on GS */
 #define X86_BUG_MONITOR                        X86_BUG(12) /* IPI required to wake up remote CPU */
 #define X86_BUG_AMD_E400               X86_BUG(13) /* CPU is among the affected by Erratum 400 */
+#define X86_BUG_CPU_INSECURE           X86_BUG(14) /* CPU is insecure and needs kernel page table isolation */
 
 #endif /* _ASM_X86_CPUFEATURES_H */

diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index c10c912..e428e16 100644 (file)
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -44,6 +44,12 @@
 # define DISABLE_LA57  (1<<(X86_FEATURE_LA57 & 31))
 #endif
 
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+# define DISABLE_PTI           0
+#else
+# define DISABLE_PTI           (1 << (X86_FEATURE_PTI & 31))
+#endif
+
 /*
  * Make sure to add features to the correct mask
  */
@@ -54,7 +60,7 @@
 #define DISABLED_MASK4 (DISABLE_PCID)
 #define DISABLED_MASK5 0
 #define DISABLED_MASK6 0
-#define DISABLED_MASK7 0
+#define DISABLED_MASK7 (DISABLE_PTI)
 #define DISABLED_MASK8 0
 #define DISABLED_MASK9 (DISABLE_MPX)
 #define DISABLED_MASK10        0

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8ddcfa4..a9210f9 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -898,6 +898,10 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
        }
 
        setup_force_cpu_cap(X86_FEATURE_ALWAYS);
+
+       /* Assume for now that ALL x86 CPUs are insecure */
+       setup_force_cpu_bug(X86_BUG_CPU_INSECURE);
+
        fpu__init_system(c);
 
 #ifdef CONFIG_X86_32