tracing: Do not assign filp->private_data to freed memory

In system_tr_open(), the filp->private_data can be assigned the 'dir'
variable even if it was freed. This is on the error path, and is
harmless because the error return code will prevent filp->private_data
from being used. But for correctness, we should not assign it to
a recently freed variable, as that can cause static tools to give
false warnings.

Also have both subsystem_open() and system_tr_open() return -ENODEV
if tracing has been disabled.

Link: http://lkml.kernel.org/r/1383764571-7318-1-git-send-email-geyslan@gmail.com

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 043f833246a0..f919a2e21bf3 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1062,6 +1062,9 @@ static int subsystem_open(struct inode *inode, struct file *filp)
         struct trace_array *tr;
         int ret;
 
+        if (tracing_is_disabled())
+                return -ENODEV;
+
         /* Make sure the system still exists */
         mutex_lock(&trace_types_lock);
         mutex_lock(&event_mutex);
@@ -1108,6 +1111,9 @@ static int system_tr_open(struct inode *inode, struct file *filp)
         struct trace_array *tr = inode->i_private;
         int ret;
 
+        if (tracing_is_disabled())
+                return -ENODEV;
+
         if (trace_array_get(tr) < 0)
                 return -ENODEV;
 
@@ -1124,11 +1130,12 @@ static int system_tr_open(struct inode *inode, struct file *filp)
         if (ret < 0) {
                 trace_array_put(tr);
                 kfree(dir);
+                return ret;
         }
 
         filp->private_data = dir;
 
-        return ret;
+        return 0;
 }
 
 static int subsystem_release(struct inode *inode, struct file *file)