[PATCH] x86: Fix potential overflow in perfctr reservation

While reviewing this code again I found a potential overflow of the bitmap.
The p4 oprofile can theoretically set bits beyond the reservation bitmap for
specific configurations. Avoid that by sizing the bitmaps properly.

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index a98ba88a8c0..9f1e8c1afab 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -41,16 +41,17 @@ int nmi_watchdog_enabled;
  *   different subsystems this reservation system just tries to coordinate
  *   things a little
  */
-static DEFINE_PER_CPU(unsigned long, perfctr_nmi_owner);
-static DEFINE_PER_CPU(unsigned long, evntsel_nmi_owner[3]);
-
-static cpumask_t backtrace_mask = CPU_MASK_NONE;
 
 /* this number is calculated from Intel's MSR_P4_CRU_ESCR5 register and it's
  * offset from MSR_P4_BSU_ESCR0.  It will be the max for all platforms (for now)
  */
 #define NMI_MAX_COUNTER_BITS 66
+#define NMI_MAX_COUNTER_LONGS BITS_TO_LONGS(NMI_MAX_COUNTER_BITS)
 
+static DEFINE_PER_CPU(unsigned long, perfctr_nmi_owner[NMI_MAX_COUNTER_LONGS]);
+static DEFINE_PER_CPU(unsigned long, evntsel_nmi_owner[NMI_MAX_COUNTER_LONGS]);
+
+static cpumask_t backtrace_mask = CPU_MASK_NONE;
 /* nmi_active:
  * >0: the lapic NMI watchdog is active, but can be disabled
  * <0: the lapic NMI watchdog has not been set up, and cannot