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From: Florian Westphal <fw@strlen.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Networking <netdev@vger.kernel.org>,
	David Ahern <dsahern@gmail.com>, Florian Westphal <fw@strlen.de>
Subject: Re: [RFC] ifa_list needs proper rcu protection
Date: Sat, 4 May 2019 20:01:39 +0200	[thread overview]
Message-ID: <20190504180139.ftpnwgefjvukda7w@breakpoint.cc> (raw)
In-Reply-To: <7bdc26e6-ce41-02ba-baef-3e4e908f6dd7@gmail.com>

Eric Dumazet <eric.dumazet@gmail.com> wrote:

Sorry for late reply.

> It looks that unless RTNL is held, accessing ifa_list needs proper RCU protection ?
> 
> indev->ifa_list can be changed under us by another cpu (which owns RTNL)
> 
> Lets took an example.
> 
> (A proper rcu_dereference() with an happy sparse support would require adding __rcu attribute,
>  I put a READ_ONCE() which should be just fine in this particular context)

I don't see e.g. __inet_insert_ifa() use rcu_assign_pointer() or similar
primitive, so I don't think its enough to change readers.

Same for __inet_del_ifa(), i see freeing gets dealyed via call_rcu, but
it uses normal assignemts instead of a rcu helper.

So, I am afraid we will have to sprinkle some rcu_assign_/derefence in
several places.


  reply	other threads:[~2019-05-04 18:01 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-25 22:50 [RFC] ifa_list needs proper rcu protection Eric Dumazet
2019-05-04 18:01 ` Florian Westphal [this message]
2019-05-04 18:06   ` Eric Dumazet

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