netdev - Re: [PATCH net] vxlan: do not destroy fdb if register

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Date:   Mon, 24 Jun 2019 21:12:01 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     David Miller <davem@...emloft.net>, Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] vxlan: do not destroy fdb if register_netdevice() is failed

On Sun, Jun 23, 2019 at 7:18 PM Taehee Yoo <ap420073@...il.com> wrote:
>
> On Mon, 24 Jun 2019 at 03:07, David Miller <davem@...emloft.net> wrote:
> >
>
> Hi David,
>
> Thank you for the review!
>
> > From: Taehee Yoo <ap420073@...il.com>
> > Date: Thu, 20 Jun 2019 20:51:08 +0900
> >
> > > __vxlan_dev_create() destroys FDB using specific pointer which indicates
> > > a fdb when error occurs.
> > > But that pointer should not be used when register_netdevice() fails because
> > > register_netdevice() internally destroys fdb when error occurs.
> > >
> > > In order to avoid un-registered dev's notification, fdb destroying routine
> > > checks dev's register status before notification.
> >
> > Simply pass do_notify as false in this failure code path of __vxlan_dev_create(),
> > thank you.
>
> Failure path of __vxlan_dev_create() can't handle do_notify in that case
> because if register_netdevice() fails it internally calls
> ->ndo_uninit() which is
> vxlan_uninit().
> vxlan_uninit() internally calls vxlan_fdb_delete_default() and it callls
> vxlan_fdb_destroy().
> do_notify of vxlan_fdb_destroy() in vxlan_fdb_delete_default() is always true.
> So, failure path of __vxlan_dev_create() doesn't have any opportunity to
> handle do_notify.


I don't see register_netdevice calling ndo_uninit in case of all
errors. In the case where it does not,
does your patch leak the fdb entry ?.

Wondering if we should just use vxlan_fdb_delete_default with a notify
flag to delete the entry if exists.
Will that help ?

There is another commit that touched this code path:
commit 6db9246871394b3a136cd52001a0763676563840

Author: Petr Machata <petrm@...lanox.com>
Date:   Tue Dec 18 13:16:00 2018 +0000
    vxlan: Fix error path in __vxlan_dev_create()