lkml.org 
[lkml]   [2013]   [Nov]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 2/2] tracing: fix referencing after memory freeing and refactors code
From
2013/11/6 Steven Rostedt <rostedt@goodmis.org>:
> Sorry for the late review, I was busy getting ready for kernel summit
> and then traveling too much.
>
No problem.

>
> On Fri, 18 Oct 2013 17:59:42 -0300
> "Geyslan G. Bem" <geyslan@gmail.com> wrote:
>
>> 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;
>
> I don't see any improvement in the above code, except for the initial
> check of tracing_is_disabled(). Just add:
>
> if (tracing_is_disabled())
> return -ENODEV;
>
> no need for all the fancy work with using ret and goto.
>
>
>> }
>>
>> @@ -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;
>>
>
> Again, we don't need the goto and err_dir. The simple fix is to finish
> the function with:
>
> ret = tracing_open_generic(inode, filp);
> if (ret < 0) {
> trace_array_put(tr);
> kfree(dir);
> return ret;
> }
>
> filp->private_data = dir;
>
> return 0;
>
> -- Steve
>
>> +err_dir:
>> + trace_array_put(tr);
>> return ret;
>> }
>>
>

Done:
[PATCH v2] tracing: fix referencing after memory freeing and refactors code


--
Regards,

Geyslan G. Bem
hackingbits.com


\
 
 \ /
  Last update: 2013-11-06 20:41    [W:0.070 / U:1.656 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site