netdev - Re: [PATCH net-next] tun: fix memory leak in error path

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Message-ID: <CANn89iKvs06pp-WR7KfUVF2mdnAyyXybfxZL5_RBKG25B6rzjw@mail.gmail.com>
Date:   Tue, 8 Oct 2019 12:47:56 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jiri Pirko <jiri@...lanox.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net-next] tun: fix memory leak in error path

On Tue, Oct 8, 2019 at 12:31 PM Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
>
> On Mon,  7 Oct 2019 12:21:05 -0700, Eric Dumazet wrote:
> > syzbot reported a warning [1] that triggered after recent Jiri patch.
> >
> > This exposes a bug that we hit already in the past (see commit
> > ff244c6b29b1 ("tun: handle register_netdevice() failures properly")
> > for details)
> >
> > tun uses priv->destructor without an ndo_init() method.
> >
> > register_netdevice() can return an error, but will
> > not call priv->destructor() in some cases. Jiri recent
> > patch added one more.
> >
> > A long term fix would be to transfer the initialization
> > of what we destroy in ->destructor() in the ndo_init()
> >
> > This looks a bit risky given the complexity of tun driver.
> >
> > A simpler fix is to detect after the failed register_netdevice()
> > if the tun_free_netdev() function was called already.
> >
> > [...]
> >
> > Fixes: ff92741270bf ("net: introduce name_node struct to be used in hashlist")
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Cc: Jiri Pirko <jiri@...lanox.com>
> > Reported-by: syzbot <syzkaller@...glegroups.com>
>
> Looks good, obviously. Presumably we could remove the workaround added
> by commit 0ad646c81b21 ("tun: call dev_get_valid_name() before
> register_netdevice()") at this point? What are your thoughts on that?

This is indeed something that could be done now, maybe by an independent revert.