ftrace: sysprof fix

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 19 insertions, 9 deletions

diff --git a/kernel/trace/trace_sysprof.c b/kernel/trace/trace_sysprof.c
index 7f6fcccffb88..f9a09fe705b0 100644
--- a/kernel/trace/trace_sysprof.c
+++ b/kernel/trace/trace_sysprof.c
@@ -37,21 +37,26 @@ struct stack_frame {
 
 static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
 {
+        int ret;
+
         if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
                 return 0;
 
-        if (__copy_from_user_inatomic(frame, frame_pointer, sizeof(*frame)))
-                return 0;
+        ret = 1;
+        pagefault_disable();
+        if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
+                ret = 0;
+        pagefault_enable();
 
-        return 1;
+        return ret;
 }
 
 static void timer_notify(struct pt_regs *regs, int cpu)
 {
-        const void __user *frame_pointer;
         struct trace_array_cpu *data;
         struct stack_frame frame;
         struct trace_array *tr;
+        const void __user *fp;
         int is_user;
         int i;
 
@@ -77,21 +82,26 @@ static void timer_notify(struct pt_regs *regs, int cpu)
 
         trace_special(tr, data, 0, current->pid, regs->ip);
 
-        frame_pointer = (void __user *)regs->bp;
+        fp = (void __user *)regs->bp;
 
         for (i = 0; i < sample_max_depth; i++) {
-                if (!copy_stack_frame(frame_pointer, &frame))
+                frame.next_fp = 0;
+                frame.return_address = 0;
+                if (!copy_stack_frame(fp, &frame))
                         break;
-                if ((unsigned long)frame_pointer < regs->sp)
+                if ((unsigned long)fp < regs->sp)
                         break;
 
                 trace_special(tr, data, 1, frame.return_address,
-                              (unsigned long)frame_pointer);
-                frame_pointer = frame.next_fp;
+                              (unsigned long)fp);
+                fp = frame.next_fp;
         }
 
         trace_special(tr, data, 2, current->pid, i);
 
+        /*
+         * Special trace entry if we overflow the max depth:
+         */
         if (i == sample_max_depth)
                 trace_special(tr, data, -1, -1, -1);
 }