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AUSCERT External Security Bulletin Redistribution
ESB-2021.1372
USN-4916-2: Linux kernel regression
22 April 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: linux kernel
Publisher: Ubuntu
Operating System: Ubuntu
Impact/Access: Execute Arbitrary Code/Commands -- Existing Account
Increased Privileges -- Existing Account
Denial of Service -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2021-29154 CVE-2021-3493
Reference: ESB-2021.1300
ESB-2021.1251
Original Bulletin:
https://ubuntu.com/security/notices/USN-4916-2
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USN-4916-2: Linux kernel regression
21 April 2021
USN-4916-1 introduced a regression in the Linux kernel.
Releases
o Ubuntu 20.04 LTS
o Ubuntu 18.04 LTS
o Ubuntu 16.04 LTS
o Ubuntu 14.04 ESM
Packages
o linux - Linux kernel
o linux-aws - Linux kernel for Amazon Web Services (AWS) systems
o linux-gke-5.3 - Linux kernel for Google Container Engine (GKE) systems
o linux-hwe - Linux hardware enablement (HWE) kernel
o linux-kvm - Linux kernel for cloud environments
o linux-lts-xenial - Linux hardware enablement kernel from Xenial for Trusty
o linux-oem-5.6 - Linux kernel for OEM systems
o linux-raspi2-5.3 - Linux kernel for Raspberry Pi (V8) systems
o linux-snapdragon - Linux kernel for Qualcomm Snapdragon processors
Details
USN-4916-1 fixed vulnerabilities in the Linux kernel. Unfortunately,
the fix for CVE-2021-3493 introduced a memory leak in some situations.
This update fixes the problem.
We apologize for the inconvenience.
Original advisory details:
It was discovered that the overlayfs implementation in the Linux kernel did
not properly validate the application of file system capabilities with
respect to user namespaces. A local attacker could use this to gain
elevated privileges. ( CVE-2021-3493 )
Piotr Krysiuk discovered that the BPF JIT compiler for x86 in the Linux
kernel did not properly validate computation of branch displacements in
some situations. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code. ( CVE-2021-29154 )
Update instructions
The problem can be corrected by updating your system to the following package
versions:
Ubuntu 20.04
o linux-image-5.6.0-1055-oem - 5.6.0-1055.59
o linux-image-oem-20.04 - 5.6.0.1055.51
Ubuntu 18.04
o linux-image-gkeop-5.3 - 5.3.0.74.131
o linux-image-gke-5.3 - 5.3.0.1043.26
o linux-image-5.3.0-74-lowlatency - 5.3.0-74.70
o linux-image-5.3.0-1040-raspi2 - 5.3.0-1040.42
o linux-image-5.3.0-74-generic - 5.3.0-74.70
o linux-image-5.3.0-1043-gke - 5.3.0-1043.46
o linux-image-raspi2-hwe-18.04 - 5.3.0.1040.29
Ubuntu 16.04
o linux-image-powerpc-smp - 4.4.0.210.216
o linux-image-4.4.0-1156-snapdragon - 4.4.0-1156.166
o linux-image-4.4.0-210-generic-lpae - 4.4.0-210.242
o linux-image-4.4.0-210-powerpc-e500mc - 4.4.0-210.242
o linux-image-4.4.0-1128-aws - 4.4.0-1128.142
o linux-image-generic - 4.4.0.210.216
o linux-image-4.4.0-210-powerpc64-emb - 4.4.0-210.242
o linux-image-powerpc-e500mc - 4.4.0.210.216
o linux-image-4.4.0-210-generic - 4.4.0-210.242
o linux-image-lowlatency - 4.4.0.210.216
o linux-image-powerpc64-emb - 4.4.0.210.216
o linux-image-generic-lpae - 4.4.0.210.216
o linux-image-powerpc64-smp - 4.4.0.210.216
o linux-image-4.4.0-210-powerpc-smp - 4.4.0-210.242
o linux-image-aws - 4.4.0.1128.133
o linux-image-snapdragon - 4.4.0.1156.148
o linux-image-4.4.0-210-lowlatency - 4.4.0-210.242
o linux-image-kvm - 4.4.0.1093.91
o linux-image-4.4.0-1093-kvm - 4.4.0-1093.102
o linux-image-4.4.0-210-powerpc64-smp - 4.4.0-210.242
o linux-image-virtual - 4.4.0.210.216
Ubuntu 14.04
o linux-image-powerpc-smp-lts-xenial - 4.4.0.210.183
o linux-image-lowlatency-lts-xenial - 4.4.0.210.183
o linux-image-4.4.0-210-lowlatency - 4.4.0-210.242~14.04.1
o linux-image-4.4.0-210-powerpc-e500mc - 4.4.0-210.242~14.04.1
o linux-image-4.4.0-210-powerpc64-emb - 4.4.0-210.242~14.04.1
o linux-image-4.4.0-210-generic - 4.4.0-210.242~14.04.1
o linux-image-powerpc-e500mc-lts-xenial - 4.4.0.210.183
o linux-image-generic-lpae-lts-xenial - 4.4.0.210.183
o linux-image-powerpc64-smp-lts-xenial - 4.4.0.210.183
o linux-image-4.4.0-1092-aws - 4.4.0-1092.96
o linux-image-powerpc64-emb-lts-xenial - 4.4.0.210.183
o linux-image-4.4.0-210-powerpc-smp - 4.4.0-210.242~14.04.1
o linux-image-aws - 4.4.0.1092.89
o linux-image-generic-lts-xenial - 4.4.0.210.183
o linux-image-4.4.0-210-generic-lpae - 4.4.0-210.242~14.04.1
o linux-image-4.4.0-210-powerpc64-smp - 4.4.0-210.242~14.04.1
o linux-image-virtual-lts-xenial - 4.4.0.210.183
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
o https://launchpad.net/bugs/1924611
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The University of Queensland
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