linux-kernel - Re: [PATCH net] tuntap: correctly handle error in tun_set

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Message-ID: <20130911105838.GA4969@redhat.com>
Date:	Wed, 11 Sep 2013 13:58:38 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	wannes rombouts <wannes.rombouts@...tech.eu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] tuntap: correctly handle error in tun_set_iff()

On Wed, Sep 11, 2013 at 01:08:04PM +0300, Michael S. Tsirkin wrote:
> 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 <wannes.rombouts@...tech.eu>
> > > > Cc: Michael S. Tsirkin <mst@...hat.com>
> > > > Signed-off-by: Jason Wang <jasowang@...hat.com>
> > > > ---
> > > > 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.

Heh I was looking at a stale tree, this is already fixed
in commit 944a1376b.

> > > 
> > > >   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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> > > 
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