[PATCH 2/2] tracing: fix referencing after memory freeing and refactors code

[Geyslan G. Bem]

In 'system_tr_open()':
Fix possible 'dir' assignment after freeing it.

In both functions:
Restructures logic conditions testing 'tracing_is_disabled()'
return before the others tests.
Centralizes the exiting in accordance to Coding Style, Chapter 7.

Signed-off-by: Geyslan G. Bem <geys...@gmail.com>
---
 kernel/trace/trace_events.c | 46 +++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 22 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 368a4d5..0f56ebf 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1060,7 +1060,10 @@ static int subsystem_open(struct inode *inode, struct 
file *filp)
        struct event_subsystem *system = NULL;
        struct ftrace_subsystem_dir *dir = NULL; /* Initialize for gcc */
        struct trace_array *tr;
-       int ret;
+       int ret = -ENODEV;
+
+       if (tracing_is_disabled())
+               return ret;
 
        /* Make sure the system still exists */
        mutex_lock(&trace_types_lock);
@@ -1082,23 +1085,21 @@ static int subsystem_open(struct inode *inode, struct 
file *filp)
        mutex_unlock(&trace_types_lock);
 
        if (!system)
-               return -ENODEV;
+               return ret;
 
        /* Some versions of gcc think dir can be uninitialized here */
        WARN_ON(!dir);
 
        /* Still need to increment the ref count of the system */
-       if (trace_array_get(tr) < 0) {
-               put_system(dir);
-               return -ENODEV;
-       }
+       ret = trace_array_get(tr);
+       if (ret)
+               goto err_get;
 
-       ret = tracing_open_generic(inode, filp);
-       if (ret < 0) {
-               trace_array_put(tr);
-               put_system(dir);
-       }
+       filp->private_data = dir;
+       return 0;
 
+err_get:
+       put_system(dir);
        return ret;
 }
 
@@ -1106,28 +1107,29 @@ static int system_tr_open(struct inode *inode, struct 
file *filp)
 {
        struct ftrace_subsystem_dir *dir;
        struct trace_array *tr = inode->i_private;
-       int ret;
+       int ret = -ENODEV;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       if (tracing_is_disabled())
+               return ret;
+
+       ret = trace_array_get(tr);
+       if (ret)
+               return ret;
 
        /* Make a temporary dir that has no system but points to tr */
        dir = kzalloc(sizeof(*dir), GFP_KERNEL);
        if (!dir) {
-               trace_array_put(tr);
-               return -ENOMEM;
+               ret = -ENOMEM;
+               goto err_dir;
        }
 
        dir->tr = tr;
 
-       ret = tracing_open_generic(inode, filp);
-       if (ret < 0) {
-               trace_array_put(tr);
-               kfree(dir);
-       }
-
        filp->private_data = dir;
+       return 0;
 
+err_dir:
+       trace_array_put(tr);
        return ret;
 }
 
-- 
1.8.4

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