CVE-2021-38203: 
CBL Mariner vulnerability analysis and mitigation

CVE-2021-38203 affects the btrfs filesystem in Linux kernel versions before 5.13.4. The vulnerability was discovered by Naohiro Aota and disclosed on August 8, 2021. The issue affects the btrfs file system implementation in the Linux kernel, specifically during allocation of new system chunks when there is a shortage of free space in the system space_info (NVD, Ubuntu).

The vulnerability is a race condition in the btrfs filesystem that can occur during the allocation of new system chunks. The issue manifests when processes trigger allocation of new system chunks during times when there is a shortage of free space in the system space_info. The vulnerability has been assigned a CVSS v3.1 Base Score of 5.5 (Medium) with a vector of CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

When successfully exploited, this vulnerability can cause a denial of service condition through a deadlock in the system. The impact is limited to local attacks and requires low privileges to execute (NetApp).

The vulnerability was fixed in Linux kernel version 5.13.4. Users should upgrade their Linux kernel to version 5.13.4 or later to address this vulnerability. The fix involves reworking the chunk allocation code to avoid deadlocks during system chunk allocation (Github).