p54: Prevent from dereferencing null pointer when releasing SKB

Added NULL check to make __dev_kfree_skb_irq consistent with kfree
family of functions.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=195289

Signed-off-by: Myungho Jung <mhjungk@gmail.com>
---
 net/core/dev.c | 3 +++
 1 file changed, 3 insertions(+)

On Thu, 2017-04-20 at 11:25 -0700, Myungho Jung wrote:
> Added NULL check to make __dev_kfree_skb_irq consistent with kfree
> family of functions.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=195289
> 
> Signed-off-by: Myungho Jung <mhjungk@gmail.com>

Hi,

I think the patch is fine but I'm confused by the subject.  You mention
p54 driver but the change is in dev.c.  I know the bugzilla references
the p54 but that's not where the change is.

Seems odd to me.

- Greg

> ---
>  net/core/dev.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 7869ae3..22be2a6 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2450,6 +2450,9 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
>  {
>  	unsigned long flags;
>  
> +	if (unlikely(!skb))
> +		return;
> +
>  	if (likely(atomic_read(&skb->users) == 1)) {
>  		smp_rmb();
>  		atomic_set(&skb->users, 0);

On Thu, Apr 20, 2017 at 04:03:43PM -0700, Greg Rose wrote:
> On Thu, 2017-04-20 at 11:25 -0700, Myungho Jung wrote:
> > Added NULL check to make __dev_kfree_skb_irq consistent with kfree
> > family of functions.
> > 
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=195289
> > 
> > Signed-off-by: Myungho Jung <mhjungk@gmail.com>
> 
> Hi,
> 
> I think the patch is fine but I'm confused by the subject.  You mention
> p54 driver but the change is in dev.c.  I know the bugzilla references
> the p54 but that's not where the change is.
> 
> Seems odd to me.
> 
> - Greg
> 
> > ---
> >  net/core/dev.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 7869ae3..22be2a6 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -2450,6 +2450,9 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
> >  {
> >  	unsigned long flags;
> >  
> > +	if (unlikely(!skb))
> > +		return;
> > +
> >  	if (likely(atomic_read(&skb->users) == 1)) {
> >  		smp_rmb();
> >  		atomic_set(&skb->users, 0);
> 
> 
> 

Hi Greg,

Thank you for checking my patch. I missed that I moved change from p54
to net/dev. Do I need to resubmit patch v2 to modify subject?

Thanks,
Myungho

On Thu, 2017-04-20 at 16:23 -0700, Myungho Jung wrote:
> On Thu, Apr 20, 2017 at 04:03:43PM -0700, Greg Rose wrote:
> > On Thu, 2017-04-20 at 11:25 -0700, Myungho Jung wrote:
> > > Added NULL check to make __dev_kfree_skb_irq consistent with kfree
> > > family of functions.
> > > 
> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=195289
> > > 
> > > Signed-off-by: Myungho Jung <mhjungk@gmail.com>
> > 
> > Hi,
> > 
> > I think the patch is fine but I'm confused by the subject.  You mention
> > p54 driver but the change is in dev.c.  I know the bugzilla references
> > the p54 but that's not where the change is.
> > 
> > Seems odd to me.
> > 
> > - Greg
> > 
> > > ---
> > >  net/core/dev.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/net/core/dev.c b/net/core/dev.c
> > > index 7869ae3..22be2a6 100644
> > > --- a/net/core/dev.c
> > > +++ b/net/core/dev.c
> > > @@ -2450,6 +2450,9 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
> > >  {
> > >  	unsigned long flags;
> > >  
> > > +	if (unlikely(!skb))
> > > +		return;
> > > +
> > >  	if (likely(atomic_read(&skb->users) == 1)) {
> > >  		smp_rmb();
> > >  		atomic_set(&skb->users, 0);
> > 
> > 
> > 
> 
> Hi Greg,
> 
> Thank you for checking my patch. I missed that I moved change from p54
> to net/dev. Do I need to resubmit patch v2 to modify subject?
> 
> Thanks,
> Myungho

Yes, I think that's the best idea.

Thanks,

- Greg