netdev - Re: Correct usage of dev_base

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20201130122129.21f9a910@hermes.local>
Date:   Mon, 30 Nov 2020 12:21:29 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Jiri Benc <jbenc@...hat.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: Correct usage of dev_base_lock in 2020

On Mon, 30 Nov 2020 21:46:17 +0200
Vladimir Oltean <olteanv@...il.com> wrote:

> On Mon, Nov 30, 2020 at 08:22:01PM +0100, Eric Dumazet wrote:
> > And ?
> >
> > A bonding device can absolutely maintain a private list, ready for
> > bonding ndo_get_stats() use, regardless
> > of register/unregister logic.
> >
> > bond_for_each_slave() is simply a macro, you can replace it by something else.  
> 
> Also, coming to take the comment at face value.
> Can it really? How? Freeing a net_device at unregister time happens
> after an RCU grace period. So whatever the bonding driver does to keep a
> private list of slave devices, those pointers need to be under RCU
> protection. And that doesn't help with the sleepable context that we're
> looking for.

if device is in a private list (in bond device), the way to handle
this is to use dev_hold() to keep a ref count.