CVE-2016-3156 (published 2016-04-27T17:59Z)

The IPv4 implementation in the Linux kernel before 4.5.2 mishandles destruction of device objects, which allows guest OS users to cause a denial of service (host OS networking outage) by arranging for a large number of IP addresses.

Severity: LOW
CVSS v2 base score: 2.1 (AV:L/AC:L/Au:N/C:N/I:N/A:P)
CVSS v3 base score: 5.5, MEDIUM (CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Weakness information:
cwe_id: CWE-399
cwe_name: Resource Management Errors
description: Weaknesses in this category are related to improper management of system resources.

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: David S. Miller
author_date: 2016-03-13 23:28:00-04:00
msg: ipv4: Don't do expensive useless work during inetdev destroy.

When an inetdev is destroyed, every address assigned to the interface
is removed.  And in this scenerio we do two pointless things which can
be very expensive if the number of assigned interfaces is large:

1) Address promotion.  We are deleting all addresses, so there is no
   point in doing this.

2) A full nf conntrack table purge for every address.  We only need to
   do this once, as is already caught by the existing
   masq_dev_notifier so masq_inet_event() can skip this.

Reported-by: Solar Designer <solar@openwall.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: devinet.c
change_type: ModificationType.MODIFY
diff: @@ -334,6 +334,9 @@ static void __inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 
 	ASSERT_RTNL();
 
+	if (in_dev->dead)
+		goto no_promotions;
+
 	/* 1. Deleting primary ifaddr forces deletion all secondaries
 	 * unless alias promotion is set
 	 **/
@@ -380,6 +383,7 @@ static void __inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 			fib_del_ifaddr(ifa, ifa1);
 	}
 
+no_promotions:
 	/* 2. Unlink it */
 
 	*ifap = ifa1->ifa_next;

programming_language: C
filename: fib_frontend.c
change_type: ModificationType.MODIFY
diff: @@ -922,6 +922,9 @@ void fib_del_ifaddr(struct in_ifaddr *ifa, struct in_ifaddr *iprim)
 		subnet = 1;
 	}
 
+	if (in_dev->dead)
+		goto no_promotions;
+
 	/* Deletion is more complicated than add.
 	 * We should take care of not to delete too much :-)
 	 *
@@ -997,6 +1000,7 @@ void fib_del_ifaddr(struct in_ifaddr *ifa, struct in_ifaddr *iprim)
 		}
 	}
 
+no_promotions:
 	if (!(ok & BRD_OK))
 		fib_magic(RTM_DELROUTE, RTN_BROADCAST, ifa->ifa_broadcast, 32, prim);
 	if (subnet && ifa->ifa_prefixlen < 31) {

programming_language: C
filename: nf_nat_masquerade_ipv4.c
change_type: ModificationType.MODIFY
diff: @@ -108,10 +108,18 @@ static int masq_inet_event(struct notifier_block *this,
 			   unsigned long event,
 			   void *ptr)
 {
-	struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
+	struct in_device *idev = ((struct in_ifaddr *)ptr)->ifa_dev;
 	struct netdev_notifier_info info;
 
-	netdev_notifier_info_init(&info, dev);
+	/* The masq_dev_notifier will catch the case of the device going
+	 * down.  So if the inetdev is dead and being destroyed we have
+	 * no work to do.  Otherwise this is an individual address removal
+	 * and we have to perform the flush.
+	 */
+	if (idev->dead)
+		return NOTIFY_DONE;
+
+	netdev_notifier_info_init(&info, idev->dev);
 	return masq_device_event(this, event, &info);
 }
 

programming_language: C