ftrace: return an error when setting a nonexistent tracer

When one try to set a nonexistent tracer, no error is returned
as if the name of the tracer was correct.
We should return -EINVAL.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index caa4051ce778bbae66e5118fd6f7e42d4ce2e3f5..78d56614c95be41f14b44c7ce4a9f90015d6bb8f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2381,9 +2381,11 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
        struct tracer *t;
        char buf[max_tracer_type_len+1];
        int i;
+       size_t ret;
 
        if (cnt > max_tracer_type_len)
                cnt = max_tracer_type_len;
+       ret = cnt;
 
        if (copy_from_user(&buf, ubuf, cnt))
                return -EFAULT;
@@ -2399,7 +2401,11 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
                if (strcmp(t->name, buf) == 0)
                        break;
        }
-       if (!t || t == current_trace)
+       if (!t) {
+               ret = -EINVAL;
+               goto out;
+       }
+       if (t == current_trace)
                goto out;
 
        if (current_trace && current_trace->reset)
@@ -2412,9 +2418,10 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
  out:
        mutex_unlock(&trace_types_lock);
 
-       filp->f_pos += cnt;
+       if (ret == cnt)
+               filp->f_pos += cnt;
 
-       return cnt;
+       return ret;
 }
 
 static ssize_t