SB2020040640 - Ubuntu update for linux, linux-hwe
Published: April 6, 2020 Updated: October 31, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 3 vulnerabilities.
1) Use-after-free (CVE-ID: CVE-2020-8428)
CWE-ID: CWE-416 - Use After Free
CVSSv4: 6.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a local user to perform a denial of service (DoS) attack.
The vulnerability exists due to a use-after-free error within the "may_create_in_sticky" in "fs/namei.c". A local user can cause a denial of service (OOPS) or possibly obtain sensitive information from kernel memory.
2) Race condition (CVE-ID: CVE-2020-8834)
CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a local user to a crash the entire system.
KVM in the Linux kernel on Power8 processors has a conflicting use of HSTATE_HOST_R1 to store r1 state in kvmppc_hv_entry plus in kvmppc_{save,restore}_tm, leading to a stack corruption. Because of this, an attacker with the ability run code in kernel space of a guest VM can cause the host kernel to panic. There were 2 commits that, according to the reporter, introduced the vulnerability: f024ee098476 ('KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures') 87a11bb6a7f7 ('KVM: PPC: Book3S HV: Work around XER[SO] bug in fake suspend mode') The former landed in 4.8, the latter in 4.17. This was fixed without realizing the impact in 4.18 with the following 3 commits, though it is believed the first is the only strictly necessary commit: 6f597c6b63b6 ('KVM: PPC: Book3S PR: Add guest MSR parameter for kvmppc_save_tm()/kvmppc_restore_tm()') 7b0e827c6970 ('KVM: PPC: Book3S HV: Factor fake-suspend handling out of kvmppc_save/restore_tm') 009c872a8bc4 ('KVM: PPC: Book3S PR: Move kvmppc_save_tm/kvmppc_restore_tm to separate file')
3) Resource exhaustion (CVE-ID: CVE-2020-8992)
CWE-ID: CWE-400 - Resource exhaustion
CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a local user to perform a denial of service (DoS) attack.
ext4_protect_reserved_inode in fs/ext4/block_validity.c in the Linux kernel through 5.5.3 allows attackers to cause a denial of service (soft lockup) via a crafted journal size.
Remediation
Install update from vendor's website.