Important kernel security update: CVE-2018-3620 and other issues; new kernel 2.6.32-042stab133.1 for Virtuozzo Containers for Linux 4.7, Server Bare Metal 5.0¶
Issue date: 2018-08-20
Applies to: Virtuozzo Containers for Linux 4.7, Server Bare Metal 5.0
Virtuozzo Advisory ID: VZA-2018-054
This update provides a new kernel 2.6.32-042stab133.1 for Virtuozzo Containers for Linux 4.7 and Server Bare Metal 5.0 that is a rebase to the Red Hat Enterprise Linux 6.10 kernel 2.6.32-754.3.5.el6. The new kernel inherits a number of security fixes from the new RHEL kernel and introduces internal stability fixes.
2. Security Fixes¶
[Important] Modern operating systems implement virtualization of physical memory to efficiently use available system resources and provide inter-domain protection through access control and isolation. The L1TF issue was found in the way the x86 microprocessor designs have implemented speculative execution of instructions (a commonly used performance optimisation) in combination with handling of page-faults caused by terminated virtual to physical address resolving process. As a result, an unprivileged attacker could use this flaw to read privileged memory of the kernel or other processes and/or cross guest/host boundaries to read host memory by conducting targeted cache side-channel attacks. (CVE-2018-3620, CVE-2018-3646)
[Important] An industry-wide issue was found in the way many modern microprocessor designs have implemented speculative execution of instructions past bounds check. The flaw relies on the presence of a precisely-defined instruction sequence in the privileged code and the fact that memory writes occur to an address which depends on the untrusted value. Such writes cause an update into the microprocessor’s data cache even for speculatively executed instructions that never actually commit (retire). As a result, an unprivileged attacker could use this flaw to influence speculative execution and/or read privileged memory by conducting targeted cache side-channel attacks. (CVE-2018-3693)
[Important] A flaw named SegmentSmack was found in the way the Linux kernel handled specially crafted TCP packets. A remote attacker could use this flaw to trigger time and calculation expensive calls to tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() functions by sending specially modified packets within ongoing TCP sessions which could lead to a CPU saturation and hence a denial of service on the system. Maintaining the denial of service condition requires continuous two-way TCP sessions to a reachable open port, thus the attacks cannot be performed using spoofed IP addresses. (CVE-2018-5390)
[Important] A flaw was found in Linux kernel’s KVM virtualization subsystem. The VMX code does not restore the GDT.LIMIT to the previous host value, but instead sets it to 64KB. With a corrupted GDT limit a host’s userspace code has an ability to place malicious entries in the GDT, particularly to the per-cpu variables. An attacker can use this to escalate their privileges. (CVE-2018-10901)
[Moderate] Use-after-free vulnerability in the snd_pcm_info() function in the ALSA subsystem in the Linux kernel allows attackers to induce a kernel memory corruption and possibly crash or lock up a system. Due to the nature of the flaw, a privilege escalation cannot be fully ruled out, although we believe it is unlikely. (CVE-2017-0861)
[Moderate] ALSA sequencer core initializes the event pool on demand by invoking snd_seq_pool_init() when the first write happens and the pool is empty. A user can reset the pool size manually via ioctl concurrently, and this may lead to UAF or out-of-bound access. (CVE-2018-7566)
[Moderate] In the Linux kernel versions 4.12, 3.10, 2.6, and possibly earlier, a race condition vulnerability exists in the sound system allowing for a potential deadlock and memory corruption due to use-after-free condition and thus denial of service. Due to the nature of the flaw, privilege escalation cannot be fully ruled out, although we believe it is unlikely. (CVE-2018-1000004)
3. Bug Fixes¶
Host could crash during restore of container with a mounted NFS share inside. (PSBM-86632)
Sctp: soft lockups caused by hb_timer getting stuck. (PSBM-86812)
‘ip neigh ls’ did not show all neighbors. (PSBM-87521)
4. Installing the Update¶
Install the update with the ‘vzup2date’ utility included in the distribution.
The JSON file with the list of new and updated packages is available at https://docs.virtuozzo.com/vza/VZA-2018-054.json.