1 files changed, 10 insertions, 1 deletions

diff --git a/arch/powerpc/mm/stab.c b/arch/powerpc/mm/stab.c
index 98cd1dc2ae75..ab5fb48b3e90 100644
--- a/arch/powerpc/mm/stab.c
+++ b/arch/powerpc/mm/stab.c
@@ -164,7 +164,7 @@ void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
 {
         struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
         struct stab_entry *ste;
-        unsigned long offset = __get_cpu_var(stab_cache_ptr);
+        unsigned long offset;
         unsigned long pc = KSTK_EIP(tsk);
         unsigned long stack = KSTK_ESP(tsk);
         unsigned long unmapped_base;
@@ -172,6 +172,15 @@ void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
         /* Force previous translations to complete. DRENG */
         asm volatile("isync" : : : "memory");
 
+        /*
+         * We need interrupts hard-disabled here, not just soft-disabled,
+         * so that a PMU interrupt can't occur, which might try to access
+         * user memory (to get a stack trace) and possible cause an STAB miss
+         * which would update the stab_cache/stab_cache_ptr per-cpu variables.
+         */
+        hard_irq_disable();
+
+        offset = __get_cpu_var(stab_cache_ptr);
         if (offset <= NR_STAB_CACHE_ENTRIES) {
                 int i;