Re: [Xen-devel] [PATCH net-next v2] xen-netfront: clean up code in xennet_release_rx_bufs

[annie li <annie.li@xxxxxxxxxx>]

On 2014-1-16 19:10, David Vrabel wrote:
> On 15/01/14 23:57, Annie Li wrote:
> > This patch implements two things:
> >
> > * release grant reference and skb for rx path, this fixex resource leaking.
> > * clean up grant transfer code kept from old netfront(2.6.18) which grants
> > pages for access/map and transfer. But grant transfer is deprecated in current
> > netfront, so remove corresponding release code for transfer.
> >
> > gnttab_end_foreign_access_ref may fail when the grant entry is currently used
> > for reading or writing. But this patch does not cover this and improvement for
> > this failure may be implemented in a separate patch.
> I don't think replacing a resource leak with a security bug is a good idea.
>
> If you would prefer not to fix the gnttab_end_foreign_access() call, I
> think you can fix this in netfront by taking a reference to the page
> before calling gnttab_end_foreign_access().  This will ensure the page
> isn't freed until the subsequent kfree_skb(), or the gref is released by
> the foreign domain (whichever is later).
What I thought is to split the implementation into two patches, this 
patch fixes the rx path resource leak(just like what tx path does), then 
a separate patch fixes gnttab_end_foreign_access_ref failure issue for 
both tx/rx through taking reference to the page before 
gnttab_end_foreign_access.
If you'd like they are posted together, I will create new patch for the 
latter and then post them.:-)
Thanks
Annie

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