An issue was discovered in Open vSwitch (OvS) 2.7.x through 2.7.6, affecting ofproto_rule_insert__ in ofproto/ofproto.c. During bundle commit, flows that are added in a bundle are applied to ofproto in order. If a flow cannot be added (e.g., the flow action is a go-to for a group id that does not exist), OvS tries to revert back all previous flows that were successfully applied from the same bundle. This is possible since OvS maintains list of old flows that were replaced by flows from the bundle. While reinserting old flows, OvS has an assertion failure due to a check on rule state != RULE_INITIALIZED. This would work for new flows, but for an old flow the rule state is RULE_REMOVED. The assertion failure causes an OvS crash.
Weakness
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openvswitch | Openvswitch | 2.7.0 (including) | 2.7.6 (including) |
| Fast Datapath for Red Hat Enterprise Linux 7 | RedHat | openvswitch-0:2.9.0-70.el7fdp.1 | * |
| Red Hat OpenStack Platform 10.0 (Newton) | RedHat | openvswitch-0:2.9.0-83.el7fdp.1 | * |
| Red Hat OpenStack Platform 13.0 (Queens) | RedHat | openvswitch-0:2.9.0-83.el7fdp.1 | * |
| Red Hat Virtualization 4.2 for Red Hat Enterprise Linux 7.6 EUS | RedHat | openvswitch-0:2.9.0-70.el7fdp.1 | * |
| Openvswitch | Ubuntu | bionic | * |
| Openvswitch | Ubuntu | esm-infra/bionic | * |
Extended Description
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.
Potential Mitigations
References
- https://access.redhat.com/errata/RHSA-2018:3500
- https://access.redhat.com/errata/RHSA-2019:0053
- https://access.redhat.com/errata/RHSA-2019:0081
- https://github.com/openvswitch/ovs/commit/0befd1f3745055c32940f5faf9559be6a14395e6
- https://usn.ubuntu.com/3873-1/
- https://access.redhat.com/errata/RHSA-2018:3500
- https://access.redhat.com/errata/RHSA-2019:0053
- https://access.redhat.com/errata/RHSA-2019:0081
- https://github.com/openvswitch/ovs/commit/0befd1f3745055c32940f5faf9559be6a14395e6
- https://usn.ubuntu.com/3873-1/