Networking: use CAP_NET_ADMIN when deciding to call request_module

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@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Paul Moore <paul.moore@hp.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: James Morris <jmorris@namei.org>

drivers/staging/comedi/comedi_fops.c

@@ -1752,12 +1752,12 @@ 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;
@@ -1770,8 +1770,8 @@ 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;
 	}

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);
 }
 

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();