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Subject[PATCH 2/2] tracing: fix referencing after memory freeing and refactors code
Date
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 <geyslan@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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