net: don't allow CAP_NET_ADMIN to load non-netdev kernel modules

Since a8f80e8ff94ecba629542d9b4b5f5a8ee3eb565c any process with
CAP_NET_ADMIN may load any module from /lib/modules/.  This doesn't mean
that CAP_NET_ADMIN is a superset of CAP_SYS_MODULE as modules are
limited to /lib/modules/**.  However, CAP_NET_ADMIN capability shouldn't
allow anybody load any module not related to networking.

This patch restricts an ability of autoloading modules to netdev modules
with explicit aliases.  This fixes CVE-2011-1019.

Arnd Bergmann suggested to leave untouched the old pre-v2.6.32 behavior
of loading netdev modules by name (without any prefix) for processes
with CAP_SYS_MODULE to maintain the compatibility with network scripts
that use autoloading netdev modules by aliases like "eth0", "wlan0".

Currently there are only three users of the feature in the upstream
kernel: ipip, ip_gre and sit.

    root@albatros:~# capsh --drop=$(seq -s, 0 11),$(seq -s, 13 34) --
    root@albatros:~# grep Cap /proc/$$/status
    CapInh:	0000000000000000
    CapPrm:	fffffff800001000
    CapEff:	fffffff800001000
    CapBnd:	fffffff800001000
    root@albatros:~# modprobe xfs
    FATAL: Error inserting xfs
    (/lib/modules/2.6.38-rc6-00001-g2bf4ca3/kernel/fs/xfs/xfs.ko): Operation not permitted
    root@albatros:~# lsmod | grep xfs
    root@albatros:~# ifconfig xfs
    xfs: error fetching interface information: Device not found
    root@albatros:~# lsmod | grep xfs
    root@albatros:~# lsmod | grep sit
    root@albatros:~# ifconfig sit
    sit: error fetching interface information: Device not found
    root@albatros:~# lsmod | grep sit
    root@albatros:~# ifconfig sit0
    sit0      Link encap:IPv6-in-IPv4
	      NOARP  MTU:1480  Metric:1

    root@albatros:~# lsmod | grep sit
    sit                    10457  0
    tunnel4                 2957  1 sit

For CAP_SYS_MODULE module loading is still relaxed:

    root@albatros:~# grep Cap /proc/$$/status
    CapInh:	0000000000000000
    CapPrm:	ffffffffffffffff
    CapEff:	ffffffffffffffff
    CapBnd:	ffffffffffffffff
    root@albatros:~# ifconfig xfs
    xfs: error fetching interface information: Device not found
    root@albatros:~# lsmod | grep xfs
    xfs                   745319  0

Reference: https://lkml.org/lkml/2011/2/24/203

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Kees Cook <kees.cook@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d971346b0340da50ae229f0dda8244f66c0eab2b..71caf7a5e6c6cc59fd975f06a0ce6bb304288d52 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2392,6 +2392,9 @@ extern int netdev_notice(const struct net_device *dev, const char *format, ...)
 extern int netdev_info(const struct net_device *dev, const char *format, ...)
        __attribute__ ((format (printf, 2, 3)));
 
+#define MODULE_ALIAS_NETDEV(device) \
+       MODULE_ALIAS("netdev-" device)
+
 #if defined(DEBUG)
 #define netdev_dbg(__dev, format, args...)                     \
        netdev_printk(KERN_DEBUG, __dev, format, ##args)

diff --git a/net/core/dev.c b/net/core/dev.c
index 8ae6631abcc2093fe2ce9929f255be7e9c1eaff1..6561021d22d1fef9b58ec54ec2b394400fb7ba25 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1114,13 +1114,21 @@ EXPORT_SYMBOL(netdev_bonding_change);
 void dev_load(struct net *net, const char *name)
 {
        struct net_device *dev;
+       int no_module;
 
        rcu_read_lock();
        dev = dev_get_by_name_rcu(net, name);
        rcu_read_unlock();
 
-       if (!dev && capable(CAP_NET_ADMIN))
-               request_module("%s", name);
+       no_module = !dev;
+       if (no_module && capable(CAP_NET_ADMIN))
+               no_module = request_module("netdev-%s", name);
+       if (no_module && capable(CAP_SYS_MODULE)) {
+               if (!request_module("%s", name))
+                       pr_err("Loading kernel module for a network device "
+"with CAP_SYS_MODULE (deprecated).  Use CAP_NET_ADMIN and alias netdev-%s "
+"instead\n", name);
+       }
 }
 EXPORT_SYMBOL(dev_load);
 

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 6613edfac28c1b10ebd9a71ef0c2f2cde479db64..d1d0e2c256fc4080033a01a621f73b1c3b080b7e 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1765,4 +1765,4 @@ module_exit(ipgre_fini);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_RTNL_LINK("gre");
 MODULE_ALIAS_RTNL_LINK("gretap");
-MODULE_ALIAS("gre0");
+MODULE_ALIAS_NETDEV("gre0");

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 988f52fba54a172bc1c49a692393f121314ba444..a5f58e7cbb26eec188786ff1324cfc540aba1ce1 100644 (file)
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -913,4 +913,4 @@ static void __exit ipip_fini(void)
 module_init(ipip_init);
 module_exit(ipip_fini);
 MODULE_LICENSE("GPL");
-MODULE_ALIAS("tunl0");
+MODULE_ALIAS_NETDEV("tunl0");

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 8ce38f10a547e68fee50a9151cfb8727770bceda..d2c16e10f650807ec32cc0502efa32cea8bc93b6 100644 (file)
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1290,4 +1290,4 @@ static int __init sit_init(void)
 module_init(sit_init);
 module_exit(sit_cleanup);
 MODULE_LICENSE("GPL");
-MODULE_ALIAS("sit0");
+MODULE_ALIAS_NETDEV("sit0");