Ubuntu Security Notice 4318-1 - Al Viro discovered that the vfs layer in the Linux kernel contained a use- after-free vulnerability. A local attacker could use this to cause a denial of service or possibly expose sensitive information. Gustavo Romero and Paul Mackerras discovered that the KVM implementation in the Linux kernel for PowerPC processors did not properly keep guest state separate from host state. A local attacker in a KVM guest could use this to cause a denial of service. Various other issues were also addressed.
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Ubuntu Security Notice USN-4318-1
April 06, 2020
linux, linux-hwe vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
Summary:
Several security issues were fixed in the Linux kernel.
Software Description:
- linux: Linux kernel
- linux-hwe: Linux hardware enablement (HWE) kernel
Details:
Al Viro discovered that the vfs layer in the Linux kernel contained a use-
after-free vulnerability. A local attacker could use this to cause a denial
of service (system crash) or possibly expose sensitive information (kernel
memory). (CVE-2020-8428)
Gustavo Romero and Paul Mackerras discovered that the KVM implementation in
the Linux kernel for PowerPC processors did not properly keep guest state
separate from host state. A local attacker in a KVM guest could use this to
cause a denial of service (host system crash). (CVE-2020-8834)
Shijie Luo discovered that the ext4 file system implementation in the Linux
kernel did not properly check for a too-large journal size. An attacker
could use this to construct a malicious ext4 image that, when mounted,
could cause a denial of service (soft lockup). (CVE-2020-8992)
Update instructions:
The problem can be corrected by updating your system to the following
package versions:
Ubuntu 18.04 LTS:
linux-image-4.15.0-96-generic 4.15.0-96.97
linux-image-4.15.0-96-generic-lpae 4.15.0-96.97
linux-image-4.15.0-96-lowlatency 4.15.0-96.97
linux-image-generic 4.15.0.96.87
linux-image-generic-lpae 4.15.0.96.87
linux-image-lowlatency 4.15.0.96.87
linux-image-powerpc-e500mc 4.15.0.96.87
linux-image-powerpc-smp 4.15.0.96.87
linux-image-powerpc64-emb 4.15.0.96.87
linux-image-powerpc64-smp 4.15.0.96.87
linux-image-virtual 4.15.0.96.87
Ubuntu 16.04 LTS:
linux-image-4.15.0-96-generic 4.15.0-96.97~16.04.1
linux-image-4.15.0-96-generic-lpae 4.15.0-96.97~16.04.1
linux-image-4.15.0-96-lowlatency 4.15.0-96.97~16.04.1
linux-image-generic-hwe-16.04 4.15.0.96.104
linux-image-generic-lpae-hwe-16.04 4.15.0.96.104
linux-image-lowlatency-hwe-16.04 4.15.0.96.104
linux-image-oem 4.15.0.96.104
linux-image-virtual-hwe-16.04 4.15.0.96.104
After a standard system update you need to reboot your computer to make
all the necessary changes.
ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.
References:
https://usn.ubuntu.com/4318-1
CVE-2020-8428, CVE-2020-8834, CVE-2020-8992
Package Information:
https://launchpad.net/ubuntu/+source/linux/4.15.0-96.97
https://launchpad.net/ubuntu/+source/linux-hwe/4.15.0-96.97~16.04.1