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

commit 8909c9ad8ff03611c9c96c9a92656213e4bb495b upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 03e8d81a839109ef149217533a7b157160fe56d9..992c700231dc9d78f0b2104d6ed2f81206624d2d 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2083,6 +2083,10 @@ static inline u32 dev_ethtool_get_flags(struct net_device *dev)
                return 0;
        return dev->ethtool_ops->get_flags(dev);
 }
+
+#define MODULE_ALIAS_NETDEV(device) \
+       MODULE_ALIAS("netdev-" device)
+
 #endif /* __KERNEL__ */
 
 #endif /* _LINUX_NETDEVICE_H */

diff --git a/net/core/dev.c b/net/core/dev.c
index 4d2f613342b9cbd125fb856e0c3ec916ce38d95c..29f936d2472922a909f6bca69c075a134ed43650 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1103,13 +1103,21 @@ 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 68c14547808a18a10ad63e0f96a29d67b0fdca00..aa70db1ccce54de81ebfc98635408ab1a58d3fa6 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1710,3 +1710,4 @@ module_exit(ipgre_fini);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_RTNL_LINK("gre");
 MODULE_ALIAS_RTNL_LINK("gretap");
+MODULE_ALIAS_NETDEV("gre0");

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index eda04fed337906fb87be32991fde83f49ff55b25..6e9168ff11daebab09d23f7213bf1cd77dfe07f3 100644 (file)
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -854,3 +854,4 @@ static void __exit ipip_fini(void)
 module_init(ipip_init);
 module_exit(ipip_fini);
 MODULE_LICENSE("GPL");
+MODULE_ALIAS_NETDEV("tunl0");

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 976e68244b998fd2a7f78536f0042fc504b083eb..51f030d492783fa21c6094ab6ce1ce7c327b0f79 100644 (file)
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1243,4 +1243,4 @@ static int __init sit_init(void)
 module_init(sit_init);
 module_exit(sit_cleanup);
 MODULE_LICENSE("GPL");
-MODULE_ALIAS("sit0");
+MODULE_ALIAS_NETDEV("sit0");