linux-kernel - Re: [PATCH 1/3] Networking: use CAP_NET_ADMIN when deciding to call request

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Message-ID: <alpine.LRH.2.00.0908140854410.11550@tundra.namei.org>
Date:	Fri, 14 Aug 2009 08:55:53 +1000 (EST)
From:	James Morris <jmorris@...ei.org>
To:	"David S. Miller" <davem@...emloft.net>
cc:	Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
	selinux@...ho.nsa.gov, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Stephen Smalley <sds@...ho.nsa.gov>,
	shemminger@...ux-foundation.org, kees@...ntu.com,
	morgan@...nel.org, Casey Schaufler <casey@...aufler-ca.com>,
	Daniel J Walsh <dwalsh@...hat.com>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH 1/3] Networking: use CAP_NET_ADMIN when deciding to call
 request_module

Any nacks/acks from netdev folk?

It looks like the right thing to me.

On Thu, 13 Aug 2009, Paul Moore wrote:

> On Thursday 13 August 2009 09:44:51 am Eric Paris wrote:
> > The networking code checks CAP_SYS_MODULE before using request_module() to
> > try to load a kernel module.  While this seems reasonable it's actually
> > weakening system security since we have to allow CAP_SYS_MODULE for things
> > like /sbin/ip and bluetoothd which need to be able to trigger module loads.
> > CAP_SYS_MODULE actually grants those binaries the ability to directly load
> > any code into the kernel.  We should instead be protecting modprobe and the
> > modules on disk, rather than granting random programs the ability to load
> > code directly into the kernel.  Instead we are going to gate those
> > networking checks on CAP_NET_ADMIN which still limits them to root but
> > which does not grant those processes the ability to load arbitrary code
> > into the kernel.
> >
> > Signed-off-by: Eric Paris <eparis@...hat.com>
> 
> Sounds and looks reasonable to me.
> 
> Acked-by: Paul Moore <paul.moore@...com>
> 
> > ---
> >
> >  drivers/staging/comedi/comedi_fops.c |    8 ++++----
> >  net/core/dev.c                       |    2 +-
> >  net/ipv4/tcp_cong.c                  |    4 ++--
> >  3 files changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/staging/comedi/comedi_fops.c
> > b/drivers/staging/comedi/comedi_fops.c index 42e4bc4..f54bb9b 100644
> > --- a/drivers/staging/comedi/comedi_fops.c
> > +++ b/drivers/staging/comedi/comedi_fops.c
> > @@ -1772,12 +1772,12 @@ static int comedi_open(struct inode *inode, struct
> > file *file) mutex_lock(&dev->mutex);
> >  	if (dev->attached)
> >  		goto ok;
> > -	if (!capable(CAP_SYS_MODULE) && dev->in_request_module) {
> > +	if (!capable(CAP_NET_ADMIN) && dev->in_request_module) {
> >  		DPRINTK("in request module\n");
> >  		mutex_unlock(&dev->mutex);
> >  		return -ENODEV;
> >  	}
> > -	if (capable(CAP_SYS_MODULE) && dev->in_request_module)
> > +	if (capable(CAP_NET_ADMIN) && dev->in_request_module)
> >  		goto ok;
> >
> >  	dev->in_request_module = 1;
> > @@ -1790,8 +1790,8 @@ static int comedi_open(struct inode *inode, struct
> > file *file)
> >
> >  	dev->in_request_module = 0;
> >
> > -	if (!dev->attached && !capable(CAP_SYS_MODULE)) {
> > -		DPRINTK("not attached and not CAP_SYS_MODULE\n");
> > +	if (!dev->attached && !capable(CAP_NET_ADMIN)) {
> > +		DPRINTK("not attached and not CAP_NET_ADMIN\n");
> >  		mutex_unlock(&dev->mutex);
> >  		return -ENODEV;
> >  	}
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 09fb03f..2604db9 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -1031,7 +1031,7 @@ void dev_load(struct net *net, const char *name)
> >  	dev = __dev_get_by_name(net, name);
> >  	read_unlock(&dev_base_lock);
> >
> > -	if (!dev && capable(CAP_SYS_MODULE))
> > +	if (!dev && capable(CAP_NET_ADMIN))
> >  		request_module("%s", name);
> >  }
> >
> > diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
> > index e92beb9..6428b34 100644
> > --- a/net/ipv4/tcp_cong.c
> > +++ b/net/ipv4/tcp_cong.c
> > @@ -116,7 +116,7 @@ int tcp_set_default_congestion_control(const char
> > *name) spin_lock(&tcp_cong_list_lock);
> >  	ca = tcp_ca_find(name);
> >  #ifdef CONFIG_MODULES
> > -	if (!ca && capable(CAP_SYS_MODULE)) {
> > +	if (!ca && capable(CAP_NET_ADMIN)) {
> >  		spin_unlock(&tcp_cong_list_lock);
> >
> >  		request_module("tcp_%s", name);
> > @@ -246,7 +246,7 @@ int tcp_set_congestion_control(struct sock *sk, const
> > char *name)
> >
> >  #ifdef CONFIG_MODULES
> >  	/* not found attempt to autoload module */
> > -	if (!ca && capable(CAP_SYS_MODULE)) {
> > +	if (!ca && capable(CAP_NET_ADMIN)) {
> >  		rcu_read_unlock();
> >  		request_module("tcp_%s", name);
> >  		rcu_read_lock();
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe
> > linux-security-module" in the body of a message to
> > majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> -- 
> paul moore
> linux @ hp
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

-- 
James Morris
<jmorris@...ei.org>
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