ACPI: Avoid array address overflow when _CST MWAIT hint bits are set

[safe/jmp/linux-2.6] / arch / x86 / kernel / acpi / cstate.c

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index c2502eb..a4805b3 100644 (file)
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -56,6 +56,7 @@ static struct cstate_entry *cpu_cstate_entry; /* per CPU ptr */
 static short mwait_supported[ACPI_PROCESSOR_MAX_POWER];
 
 #define MWAIT_SUBSTATE_MASK    (0xf)
+#define MWAIT_CSTATE_MASK      (0xf)
 #define MWAIT_SUBSTATE_SIZE    (4)
 
 #define CPUID_MWAIT_LEAF (5)
@@ -98,7 +99,8 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
        cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 
        /* Check whether this particular cx_type (in CST) is supported or not */
-       cstate_type = (cx->address >> MWAIT_SUBSTATE_SIZE) + 1;
+       cstate_type = ((cx->address >> MWAIT_SUBSTATE_SIZE) &
+                       MWAIT_CSTATE_MASK) + 1;
        edx_part = edx >> (cstate_type * MWAIT_SUBSTATE_SIZE);
        num_cstate_subtype = edx_part & MWAIT_SUBSTATE_MASK;