[PATCH]s390/char/vmur.c: memory leak Fix in the driver

[PATCH]s390/char/vmur.c: memory leak Fix in the driver

[Chen, Dennis (SRDC SW)]

This patch is used to fix a memory leak issue in s390/char/vmur.c: a character device instance is 
allocated by cdev_alloc, the cdev_del will not free that space if cdev_init is applied before. 

Signed-off-by: dennis1.chen@amd.com
--- a/s390/char/vmur.c  2012-03-18 02:50:47.950963949 +0800
+++ b/s390/char/vmur.c  2012-03-18 03:12:04.790936740 +0800
@@ -903,7 +903,7 @@ static int ur_set_online(struct ccw_devi
                goto fail_urdev_put;
        }

-       cdev_init(urd->char_device, &ur_fops);
+       urd->char_device->ops = &ur_fops;
        urd->char_device->dev = MKDEV(major, minor);
        urd->char_device->owner = ur_fops.owner;

RE: [PATCH]s390/char/vmur.c: memory leak Fix in the driver

[Chen, Dennis (SRDC SW)]

CC'ing maintainer: Martin Schwidefsky &  Heiko Carstens...

-----Original Message-----
From: Chen, Dennis (SRDC SW) 
Sent: Sunday, March 18, 2012 3:41 AM
To: linux-kernel@vger.kernel.org
Cc: beattiem@uk.ibm.com; holzheu@de.ibm.com; munzert@de.ibm.com; linux390@de.ibm.com; linux-s390@vger.kernel.org; Chen, Dennis (SRDC SW)
Subject: [PATCH]s390/char/vmur.c: memory leak Fix in the driver

This patch is used to fix a memory leak issue in s390/char/vmur.c: a character device instance is 
allocated by cdev_alloc, the cdev_del will not free that space if cdev_init is applied before. 

Signed-off-by: dennis1.chen@amd.com
--- a/s390/char/vmur.c  2012-03-18 02:50:47.950963949 +0800
+++ b/s390/char/vmur.c  2012-03-18 03:12:04.790936740 +0800
@@ -903,7 +903,7 @@ static int ur_set_online(struct ccw_devi
                goto fail_urdev_put;
        }

-       cdev_init(urd->char_device, &ur_fops);
+       urd->char_device->ops = &ur_fops;
        urd->char_device->dev = MKDEV(major, minor);
        urd->char_device->owner = ur_fops.owner;

Re: [PATCH]s390/char/vmur.c: memory leak Fix in the driver

[Martin Schwidefsky]

On Mon, 19 Mar 2012 01:55:40 +0000
"Chen, Dennis (SRDC SW)" <Dennis1.Chen@amd.com> wrote:

> CC'ing maintainer: Martin Schwidefsky &  Heiko Carstens...
> 
> -----Original Message-----
> From: Chen, Dennis (SRDC SW) 
> Sent: Sunday, March 18, 2012 3:41 AM
> To: linux-kernel@vger.kernel.org
> Cc: beattiem@uk.ibm.com; holzheu@de.ibm.com; munzert@de.ibm.com; linux390@de.ibm.com; linux-s390@vger.kernel.org; Chen, Dennis (SRDC SW)
> Subject: [PATCH]s390/char/vmur.c: memory leak Fix in the driver
> 
> This patch is used to fix a memory leak issue in s390/char/vmur.c: a character device instance is 
> allocated by cdev_alloc, the cdev_del will not free that space if cdev_init is applied before. 
> 
> Signed-off-by: dennis1.chen@amd.com
> --- a/s390/char/vmur.c  2012-03-18 02:50:47.950963949 +0800
> +++ b/s390/char/vmur.c  2012-03-18 03:12:04.790936740 +0800
> @@ -903,7 +903,7 @@ static int ur_set_online(struct ccw_devi
>                 goto fail_urdev_put;
>         }
> 
> -       cdev_init(urd->char_device, &ur_fops);
> +       urd->char_device->ops = &ur_fops;
>         urd->char_device->dev = MKDEV(major, minor);
>         urd->char_device->owner = ur_fops.owner;
> 

How does that fix anything? My copy of cdev_init looks like this:

void cdev_init(struct cdev *cdev, const struct file_operations *fops)
{
        memset(cdev, 0, sizeof *cdev);
        INIT_LIST_HEAD(&cdev->list);
        kobject_init(&cdev->kobj, &ktype_cdev_default);
        cdev->ops = fops;
}

It does not allocate anything but it initializes some more fields.
The new code would only initialize the ops field. In addition
cdev_del does a kobject_put and the release function of the object
will call cdev_dynamic_release as far as I can tell. That code
should be fine as it is.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

Re: [PATCH]s390/char/vmur.c: memory leak Fix in the driver

[Martin Schwidefsky]

On Mon, 19 Mar 2012 11:37:44 +0100
Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:

> On Mon, 19 Mar 2012 01:55:40 +0000
> "Chen, Dennis (SRDC SW)" <Dennis1.Chen@amd.com> wrote:
> 
> > CC'ing maintainer: Martin Schwidefsky &  Heiko Carstens...
> > 
> > -----Original Message-----
> > From: Chen, Dennis (SRDC SW) 
> > Sent: Sunday, March 18, 2012 3:41 AM
> > To: linux-kernel@vger.kernel.org
> > Cc: beattiem@uk.ibm.com; holzheu@de.ibm.com; munzert@de.ibm.com; linux390@de.ibm.com; linux-s390@vger.kernel.org; Chen, Dennis (SRDC SW)
> > Subject: [PATCH]s390/char/vmur.c: memory leak Fix in the driver
> > 
> > This patch is used to fix a memory leak issue in s390/char/vmur.c: a character device instance is 
> > allocated by cdev_alloc, the cdev_del will not free that space if cdev_init is applied before. 
> > 
> > Signed-off-by: dennis1.chen@amd.com
> > --- a/s390/char/vmur.c  2012-03-18 02:50:47.950963949 +0800
> > +++ b/s390/char/vmur.c  2012-03-18 03:12:04.790936740 +0800
> > @@ -903,7 +903,7 @@ static int ur_set_online(struct ccw_devi
> >                 goto fail_urdev_put;
> >         }
> > 
> > -       cdev_init(urd->char_device, &ur_fops);
> > +       urd->char_device->ops = &ur_fops;
> >         urd->char_device->dev = MKDEV(major, minor);
> >         urd->char_device->owner = ur_fops.owner;
> > 
> 
> How does that fix anything? My copy of cdev_init looks like this:
> 
> void cdev_init(struct cdev *cdev, const struct file_operations *fops)
> {
>         memset(cdev, 0, sizeof *cdev);
>         INIT_LIST_HEAD(&cdev->list);
>         kobject_init(&cdev->kobj, &ktype_cdev_default);
>         cdev->ops = fops;
> }
> 
> It does not allocate anything but it initializes some more fields.
> The new code would only initialize the ops field. In addition
> cdev_del does a kobject_put and the release function of the object
> will call cdev_dynamic_release as far as I can tell. That code
> should be fine as it is.

Hmm, forget that. cdev_init has a second kobject_init that replaces
ktype_cdev_dynamic with ktype_cdev_default. cdev_alloc already does
the initialization and your fix is just fine. 
Seems like cdev_init is only there for static cdev structures.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

RE: [PATCH]s390/char/vmur.c: memory leak Fix in the driver

[Chen, Dennis (SRDC SW)]

On Mon, Mar 19, 2012 at 7:08 PM, Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
> On Mon, 19 Mar 2012 11:37:44 +0100
> Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
>
>> On Mon, 19 Mar 2012 01:55:40 +0000
>> "Chen, Dennis (SRDC SW)" <Dennis1.Chen@amd.com> wrote:
>>
>> > CC'ing maintainer: Martin Schwidefsky &  Heiko Carstens...
>> >
>> > -----Original Message-----
>> > From: Chen, Dennis (SRDC SW)
>> > Sent: Sunday, March 18, 2012 3:41 AM
>> > To: linux-kernel@vger.kernel.org
>> > Cc: beattiem@uk.ibm.com; holzheu@de.ibm.com; munzert@de.ibm.com; linux390@de.ibm.com; linux-s390@vger.kernel.org; Chen, Dennis (SRDC SW)
>> > Subject: [PATCH]s390/char/vmur.c: memory leak Fix in the driver
>> >
>> > This patch is used to fix a memory leak issue in s390/char/vmur.c: a character device instance is
>> > allocated by cdev_alloc, the cdev_del will not free that space if cdev_init is applied before.
>> >
>> > Signed-off-by: dennis1.chen@amd.com
>> > --- a/s390/char/vmur.c  2012-03-18 02:50:47.950963949 +0800
>> > +++ b/s390/char/vmur.c  2012-03-18 03:12:04.790936740 +0800
>> > @@ -903,7 +903,7 @@ static int ur_set_online(struct ccw_devi
>> >                 goto fail_urdev_put;
>> >         }
>> >
>> > -       cdev_init(urd->char_device, &ur_fops);
>> > +       urd->char_device->ops = &ur_fops;
>> >         urd->char_device->dev = MKDEV(major, minor);
>> >         urd->char_device->owner = ur_fops.owner;
>> >
>>
>> How does that fix anything? My copy of cdev_init looks like this:
>>
>> void cdev_init(struct cdev *cdev, const struct file_operations *fops)
>> {
>>         memset(cdev, 0, sizeof *cdev);
>>         INIT_LIST_HEAD(&cdev->list);
>>         kobject_init(&cdev->kobj, &ktype_cdev_default);
>>         cdev->ops = fops;
>> }
>>
>> It does not allocate anything but it initializes some more fields.
>> The new code would only initialize the ops field. In addition
>> cdev_del does a kobject_put and the release function of the object
>> will call cdev_dynamic_release as far as I can tell. That code
>> should be fine as it is.
>
> Hmm, forget that. cdev_init has a second kobject_init that replaces
> ktype_cdev_dynamic with ktype_cdev_default. cdev_alloc already does
> the initialization and your fix is just fine.
> Seems like cdev_init is only there for static cdev structures.
>
> --

Yes, you're right. So if we don't have this patch, all the cdev instance allocated by cdev_alloc() will not freed by cdev_del as expected,
if the system running with long enough time, memory will exhaust, especially for a server platform...