diff mbox series

[01/11] kset: fix documentation for kset_register()

Message ID 20221021022102.2231464-2-yangyingliang@huawei.com (mailing list archive)
State New
Headers show
Series fix memory leak while kset_register() fails | expand

Commit Message

Yang Yingliang Oct. 21, 2022, 2:20 a.m. UTC
kset_register() is currently used in some places without calling
kset_put() in error path, because the callers think it should be
kset internal thing to do, but the driver core can not know what
caller doing with that memory at times. The memory could be freed
both in kset_put() and error path of caller, if it is called in
kset_register().

So make the function documentation more explicit about calling
kset_put() in the error path of caller.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 lib/kobject.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Luben Tuikov Oct. 21, 2022, 5:34 a.m. UTC | #1
On 2022-10-20 22:20, Yang Yingliang wrote:
> kset_register() is currently used in some places without calling
> kset_put() in error path, because the callers think it should be
> kset internal thing to do, but the driver core can not know what
> caller doing with that memory at times. The memory could be freed
> both in kset_put() and error path of caller, if it is called in
> kset_register().
> 
> So make the function documentation more explicit about calling
> kset_put() in the error path of caller.
> 
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  lib/kobject.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/kobject.c b/lib/kobject.c
> index a0b2dbfcfa23..6da04353d974 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -834,6 +834,9 @@ EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
>  /**
>   * kset_register() - Initialize and add a kset.
>   * @k: kset.
> + *
> + * If this function returns an error, kset_put() must be called to
> + * properly clean up the memory associated with the object.
>   */

And I'd continue the sentence, with " ... with the object,
for instance the memory for the kset.kobj.name when kobj_set_name(&kset.kobj, format, ...)
was called before calling kset_register()."

This makes it clear what we want to make sure is freed, in case of an early error
from kset_register().

Regards,
Luben

>  int kset_register(struct kset *k)
>  {
Yang Yingliang Oct. 21, 2022, 8:05 a.m. UTC | #2
On 2022/10/21 13:34, Luben Tuikov wrote:
> On 2022-10-20 22:20, Yang Yingliang wrote:
>> kset_register() is currently used in some places without calling
>> kset_put() in error path, because the callers think it should be
>> kset internal thing to do, but the driver core can not know what
>> caller doing with that memory at times. The memory could be freed
>> both in kset_put() and error path of caller, if it is called in
>> kset_register().
>>
>> So make the function documentation more explicit about calling
>> kset_put() in the error path of caller.
>>
>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   lib/kobject.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/lib/kobject.c b/lib/kobject.c
>> index a0b2dbfcfa23..6da04353d974 100644
>> --- a/lib/kobject.c
>> +++ b/lib/kobject.c
>> @@ -834,6 +834,9 @@ EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
>>   /**
>>    * kset_register() - Initialize and add a kset.
>>    * @k: kset.
>> + *
>> + * If this function returns an error, kset_put() must be called to
>> + * properly clean up the memory associated with the object.
>>    */
> And I'd continue the sentence, with " ... with the object,
> for instance the memory for the kset.kobj.name when kobj_set_name(&kset.kobj, format, ...)
> was called before calling kset_register()."
kobject_cleanup() not only frees name, but aslo calls ->release() to 
free another resources.
>
> This makes it clear what we want to make sure is freed, in case of an early error
> from kset_register().

How about like this:

If this function returns an error, kset_put() must be called to clean up the name of
kset object and other memory associated with the object.

>
> Regards,
> Luben
>
>>   int kset_register(struct kset *k)
>>   {
> .
Greg Kroah-Hartman Oct. 21, 2022, 8:16 a.m. UTC | #3
On Fri, Oct 21, 2022 at 04:05:18PM +0800, Yang Yingliang wrote:
> 
> On 2022/10/21 13:34, Luben Tuikov wrote:
> > On 2022-10-20 22:20, Yang Yingliang wrote:
> > > kset_register() is currently used in some places without calling
> > > kset_put() in error path, because the callers think it should be
> > > kset internal thing to do, but the driver core can not know what
> > > caller doing with that memory at times. The memory could be freed
> > > both in kset_put() and error path of caller, if it is called in
> > > kset_register().
> > > 
> > > So make the function documentation more explicit about calling
> > > kset_put() in the error path of caller.
> > > 
> > > Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> > > ---
> > >   lib/kobject.c | 3 +++
> > >   1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/lib/kobject.c b/lib/kobject.c
> > > index a0b2dbfcfa23..6da04353d974 100644
> > > --- a/lib/kobject.c
> > > +++ b/lib/kobject.c
> > > @@ -834,6 +834,9 @@ EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
> > >   /**
> > >    * kset_register() - Initialize and add a kset.
> > >    * @k: kset.
> > > + *
> > > + * If this function returns an error, kset_put() must be called to
> > > + * properly clean up the memory associated with the object.
> > >    */
> > And I'd continue the sentence, with " ... with the object,
> > for instance the memory for the kset.kobj.name when kobj_set_name(&kset.kobj, format, ...)
> > was called before calling kset_register()."
> kobject_cleanup() not only frees name, but aslo calls ->release() to free
> another resources.

Yes, but it's the kobject of the kset, which does need to have it's name
cleaned up, but that kobject should NOT be freeing any larger structures
that the kset might be embedded in, right?

> > This makes it clear what we want to make sure is freed, in case of an early error
> > from kset_register().
> 
> How about like this:
> 
> If this function returns an error, kset_put() must be called to clean up the name of
> kset object and other memory associated with the object.

Again, I think we can fix this up to not be needed.

thanks,

greg k-h
Luben Tuikov Oct. 21, 2022, 8:18 a.m. UTC | #4
On 2022-10-21 04:05, Yang Yingliang wrote:
> 
> On 2022/10/21 13:34, Luben Tuikov wrote:
>> On 2022-10-20 22:20, Yang Yingliang wrote:
>>> kset_register() is currently used in some places without calling
>>> kset_put() in error path, because the callers think it should be
>>> kset internal thing to do, but the driver core can not know what
>>> caller doing with that memory at times. The memory could be freed
>>> both in kset_put() and error path of caller, if it is called in
>>> kset_register().
>>>
>>> So make the function documentation more explicit about calling
>>> kset_put() in the error path of caller.
>>>
>>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>>> ---
>>>   lib/kobject.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/lib/kobject.c b/lib/kobject.c
>>> index a0b2dbfcfa23..6da04353d974 100644
>>> --- a/lib/kobject.c
>>> +++ b/lib/kobject.c
>>> @@ -834,6 +834,9 @@ EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
>>>   /**
>>>    * kset_register() - Initialize and add a kset.
>>>    * @k: kset.
>>> + *
>>> + * If this function returns an error, kset_put() must be called to
>>> + * properly clean up the memory associated with the object.
>>>    */
>> And I'd continue the sentence, with " ... with the object,
>> for instance the memory for the kset.kobj.name when kobj_set_name(&kset.kobj, format, ...)
>> was called before calling kset_register()."
> kobject_cleanup() not only frees name, but aslo calls ->release() to 
> free another resources.

Yes, it does. For this reason I said "for instance..." I didn't want to include
this in case in the future if the code changes, the comment would be wrong. IOW,
I wanted to add the minimalist comment possible.

>>
>> This makes it clear what we want to make sure is freed, in case of an early error
>> from kset_register().
> 
> How about like this:
> 
> If this function returns an error, kset_put() must be called to clean up the name of
> kset object and other memory associated with the object.

It's bit too wordy and redundant with what else it does--this can be gleaned
from the code. I'd say:

	On error, kset_put() should be called to clean up at least kset.kobj.name allocated
	by kobj_set_name(&kset.kobj, format, ...).

This tells the reader the symmetry of the calls: kobj_set_name() --> kset_register() --> kset_put();
Because if the code evolves to use other means of allocation, or if the the user allocates a name
by different means, then they'll understand what to watch out for.

Regards,
Luben

> 
>>
>> Regards,
>> Luben
>>
>>>   int kset_register(struct kset *k)
>>>   {
>> .
diff mbox series

Patch

diff --git a/lib/kobject.c b/lib/kobject.c
index a0b2dbfcfa23..6da04353d974 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -834,6 +834,9 @@  EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
 /**
  * kset_register() - Initialize and add a kset.
  * @k: kset.
+ *
+ * If this function returns an error, kset_put() must be called to
+ * properly clean up the memory associated with the object.
  */
 int kset_register(struct kset *k)
 {