netdev - Re: [PATCH net] ipv4: igmp: fix a use after free

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Message-ID: <1496972227.736.90.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 08 Jun 2017 18:37:07 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Xin Long <lucien.xin@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] ipv4: igmp: fix a use after free

On Thu, 2017-06-08 at 17:59 -0700, Cong Wang wrote:
> On Thu, Jun 8, 2017 at 1:33 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > I mentioned (in https://lkml.org/lkml/2017/5/31/619 ) that we might need
> > to defer freeing after rcu grace period but for some reason decided it
> > was not needed.
> 
> This one makes sense, it is the second time I saw the use-after-free
> in igmp code, both are because we don't respect the RCU rule to free
> an element in the list.
> 
> >
> > What about :
> 
> But not sure if all ip_ma_put() callers want ip_mc_clear_src().

That would lead to a memory leak if this was the case ?