Subject: Re: [PATCH net] tuntap: correctly handle error in tun_set_iff()

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 11 Sep 2013 13:08:04 +0300

On Wed, Sep 11, 2013 at 05:55:04AM -0400, Jason Wang wrote:
> 
> 
> ----- Original Message -----
> > On Wed, Sep 11, 2013 at 04:24:05PM +0800, Jason Wang wrote:
> > > Commit c8d68e6be1c3b242f1c598595830890b65cea64a (tuntap: multiqueue
> > > support)
> > > only call free_netdev() on err in tun_set_iff(). This causes several
> > > issues:
> > > 
> > > - memory of tun security were leaked
> > 
> > Not just tun security -  sock reference too (didn't detach)
> > 
> 
> Yes, I mention it in the next item.

That line's a bit too long btw.
Keep it under 70 chars for commit logs.

> > > - use after free since the flow gc timer was not deleted and the tfile were
> > > not
> > >   detached
> > > 
> > > This patch solves the above issues.
> > > 
> > > Reported-by: Wannes Rombouts <[email-masked]>
> > > Cc: Michael S. Tsirkin <[email-masked]>
> > > Signed-off-by: Jason Wang <[email-masked]>
> > > ---
> > > The patch were also needed for stable 3.8+.
> > > ---
> > >  drivers/net/tun.c |    9 +++++++--
> > >  1 files changed, 7 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > > index a639de8..e5fb5d3 100644
> > > --- a/drivers/net/tun.c
> > > +++ b/drivers/net/tun.c
> > > @@ -1641,11 +1641,11 @@ static int tun_set_iff(struct net *net, struct file
> > > *file, struct ifreq *ifr)
> > >  		INIT_LIST_HEAD(&tun->disabled);
> > >  		err = tun_attach(tun, file, false);
> > >  		if (err < 0)
> > > -			goto err_free_dev;
> > > +			goto err_free_flow;
> > >  
> > >  		err = register_netdevice(tun->dev);
> > >  		if (err < 0)
> > > -			goto err_free_dev;
> > > +			goto err_detach;
> > >  
> > >  		if (device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
> > >  		    device_create_file(&tun->dev->dev, &dev_attr_owner) ||
> > > @@ -1689,6 +1689,11 @@ static int tun_set_iff(struct net *net, struct file
> > > *file, struct ifreq *ifr)
> > >  	strcpy(ifr->ifr_name, tun->dev->name);
> > >  	return 0;
> > >  
> > > +err_detach:
> > > +	tun_detach_all(dev);
> > > +err_free_flow:
> > > +	tun_flow_uninit(tun);
> > > +	security_tun_dev_free_security(tun->security);
> > 
> > This bit looks wrong: if flow_init fails, we
> > need security_tun_dev_free_security, don't we?
> > I think we need:
> > 	+err_free_sec:	security_tun_dev_free_security(tun->security);
> > and goto here on flow_init failures.
> 
> tun_flow_init() always succeed. So we're ok here.

True. So please make it return void then.

> > 
> > >   err_free_dev:
> > 
> > Pls shift this one 1 space left for consistency.
> > 
> 
> Ok.
> > >  	free_netdev(dev);
> > >  	return err;
> > > --
> > > 1.7.1
> > --
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