[net,v3] driver: veth: Fix one possbile memleak when fail to register_netdevice

From: Gao Feng <gfree.wind@foxmail.com>

The veth driver allocates some resources in its ndo_init func, and
free them in its destructor func. Then there is one memleak that some
errors happen after register_netdevice invokes the ndo_init callback.
Because the destructor would not be invoked to free the resources.

Now create one new func veth_destructor_free to free the mem in the
destructor, and add ndo_uninit func also invokes it when fail to register
the veth device.

It's not only free all resources, but also follow the original desgin
that the resources are freed in the destructor normally after
register the device successfully.

Signed-off-by: Gao Feng <gfree.wind@foxmail.com>
---
 v3: Split one patch to multiple commits, per David Ahern
 v2: Move the free in ndo_uninit when fail to register, per Herbert Xu
 v1: initial version

 drivers/net/veth.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

On 4/28/17 9:51 PM, gfree.wind@foxmail.com wrote:
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 8c39d6d..418376a 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -224,9 +224,21 @@ static int veth_dev_init(struct net_device *dev)
>  	return 0;
>  }
>  
> -static void veth_dev_free(struct net_device *dev)
> +static void veth_destructor_free(struct net_device *dev)

_destructor in the name is confusing since veth_dev_free is the
dev->destructor. Perhaps that should be veth_free_stats.


>  {
>  	free_percpu(dev->vstats);
> +}
> +
> +static void veth_dev_uninit(struct net_device *dev)
> +{
> +	/* dev is not registered, perform the free instead of destructor */
> +	if (dev->reg_state == NETREG_UNINITIALIZED)
> +		veth_destructor_free(dev);
> +}
> +
> +static void veth_dev_free(struct net_device *dev)
> +{
> +	veth_destructor_free(dev);
>  	free_netdev(dev);
>  }
>  
> @@ -284,6 +296,7 @@ static void veth_set_rx_headroom(struct net_device *dev, int new_hr)
>  
>  static const struct net_device_ops veth_netdev_ops = {
>  	.ndo_init            = veth_dev_init,
> +	.ndo_uninit          = veth_dev_uninit,
>  	.ndo_open            = veth_open,
>  	.ndo_stop            = veth_close,
>  	.ndo_start_xmit      = veth_xmit,
> 

Functionally, it looks good to me.

Acked-by: David Ahern <dsa@cumulusnetworks.com>

On Sat, Apr 29, 2017 at 11:51 AM,  <gfree.wind@foxmail.com> wrote:
> From: Gao Feng <gfree.wind@foxmail.com>
>
> The veth driver allocates some resources in its ndo_init func, and
> free them in its destructor func. Then there is one memleak that some
> errors happen after register_netdevice invokes the ndo_init callback.
> Because the destructor would not be invoked to free the resources.
>
> Now create one new func veth_destructor_free to free the mem in the
> destructor, and add ndo_uninit func also invokes it when fail to register
> the veth device.
>
> It's not only free all resources, but also follow the original desgin
> that the resources are freed in the destructor normally after
> register the device successfully.
>
> Signed-off-by: Gao Feng <gfree.wind@foxmail.com>
> ---
>  v3: Split one patch to multiple commits, per David Ahern
>  v2: Move the free in ndo_uninit when fail to register, per Herbert Xu
>  v1: initial version
>
>  drivers/net/veth.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 8c39d6d..418376a 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -224,9 +224,21 @@ static int veth_dev_init(struct net_device *dev)
>         return 0;
>  }
>
> -static void veth_dev_free(struct net_device *dev)
> +static void veth_destructor_free(struct net_device *dev)
>  {
>         free_percpu(dev->vstats);
> +}
not sure why you needed to add this function.
to use free_percpu() directly may be clearer.

> +
> +static void veth_dev_uninit(struct net_device *dev)
> +{
call free_percpu() here, no need to check dev->reg_state.
free_percpu will just return if dev->vstats is NULL.

> +       /* dev is not registered, perform the free instead of destructor */
> +       if (dev->reg_state == NETREG_UNINITIALIZED)
> +               veth_destructor_free(dev);
> +}
> +
> +static void veth_dev_free(struct net_device *dev)
> +{
> +       veth_destructor_free(dev);
use free_percpu here as well.

>         free_netdev(dev);
>  }
>
> @@ -284,6 +296,7 @@ static void veth_set_rx_headroom(struct net_device *dev, int new_hr)
>
>  static const struct net_device_ops veth_netdev_ops = {
>         .ndo_init            = veth_dev_init,
> +       .ndo_uninit          = veth_dev_uninit,
>         .ndo_open            = veth_open,
>         .ndo_stop            = veth_close,
>         .ndo_start_xmit      = veth_xmit,
> --
> 2.7.4
>

> From: David Ahern [mailto:dsa@cumulusnetworks.com]
> Sent: Monday, May 1, 2017 11:08 PM
> On 4/28/17 9:51 PM, gfree.wind@foxmail.com wrote:
> > diff --git a/drivers/net/veth.c b/drivers/net/veth.c index
> > 8c39d6d..418376a 100644
> > --- a/drivers/net/veth.c
> > +++ b/drivers/net/veth.c
> > @@ -224,9 +224,21 @@ static int veth_dev_init(struct net_device *dev)
> >  	return 0;
> >  }
> >
> > -static void veth_dev_free(struct net_device *dev)
> > +static void veth_destructor_free(struct net_device *dev)
> 
> _destructor in the name is confusing since veth_dev_free is the
> dev->destructor. Perhaps that should be veth_free_stats.

Because I want to emphasize it should be invoked in the destructor.
What's your opinion ?


[...]
> Functionally, it looks good to me.
> 
> Acked-by: David Ahern <dsa@cumulusnetworks.com>

Thanks David.
I have sent the v4 patches with a series according to David's advice.

BTW, because I send multiple patches too fast today, the email server blocks
my account.
So I have to reply you with a different email account. Sorry.

Regards
Feng

> From: Xin Long [mailto:lucien.xin@gmail.com]
> Sent: Tuesday, May 2, 2017 3:56 PM
> On Sat, Apr 29, 2017 at 11:51 AM,  <gfree.wind@foxmail.com> wrote:
> > From: Gao Feng <gfree.wind@foxmail.com>
[...]
> > -static void veth_dev_free(struct net_device *dev)
> > +static void veth_destructor_free(struct net_device *dev)
> >  {
> >         free_percpu(dev->vstats);
> > +}
> not sure why you needed to add this function.
> to use free_percpu() directly may be clearer.

Because both of ndo_uninit and destructor need to perform same free statements.
It is good at maintain the codes with the common function.
> 
> > +
> > +static void veth_dev_uninit(struct net_device *dev) {
> call free_percpu() here, no need to check dev->reg_state.
> free_percpu will just return if dev->vstats is NULL.

It would break the original design if don't check the reg_state.
The original logic is that free the resources in the destructor, not in ndo_init.

BTW, because I send multiple patches too fast today, the email server blocks my account.
So I have to reply you with a different email account. Sorry.

Best Regards
Feng

> 
[...]