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 d8fd2c23a1b994ec10e0a204820d6c7daf7dca0e..e63d08b0668b0ed20016f133e63b787531723962 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2336,6 +2336,9 @@ 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 c0d3b5f68e1eb29306f19da749297a5267fb155d..1f03c4f6ef1a2b1cf6caad6f882f29d4c736cc44 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1116,13 +1116,21 @@ 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 70ff77f02eee3b345fa94efd35563a95b2b582ef..c0bbbc807c8a52ffb753ce8e8bafaf66612206dd 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1775,3 +1775,4 @@ 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 cd300aaee78f542630f40ab9a34f9b10af8eec9e..b472da92047407faa1ff1cb67a506bee925150f2 100644 (file)
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -921,3 +921,4 @@ 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 8c4d00c7cd2bb030c194c19e00b5455d2cddf3df..b77006139966cb68e1e2165dc62b3d593724f4e4 100644 (file)
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1292,4 +1292,4 @@ static int __init sit_init(void)
 module_init(sit_init);
 module_exit(sit_cleanup);
 MODULE_LICENSE("GPL");
-MODULE_ALIAS("sit0");
+MODULE_ALIAS_NETDEV("sit0");