CVE-2022-2938: 
Linux Kernel vulnerability analysis and mitigation

A vulnerability was discovered in the Linux kernel's implementation of Pressure Stall Information (PSI), identified as CVE-2022-2938. The flaw, while disabled by default, was found in Linux kernel versions prior to 5.17. The vulnerability was reported in August 2022 and could potentially allow attackers to compromise system security (NVD, MITRE).

The vulnerability stems from a use-after-free (UAF) issue in the PSI trigger mechanism when it is destroyed while being polled. The issue occurs because the lifetime of the waitqueue becomes arbitrary when write operations on PSI files replace old triggers with new ones. When overwriting an existing trigger, its waitqueue is freed, causing pending poll() operations to encounter issues with the destroyed event_wait (Kernel Commit). The vulnerability has been assigned a CVSS score of 7.8 (HIGH) with the vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NetApp Advisory).

Successful exploitation of this vulnerability could lead to system crashes, memory corruption side effects, disclosure of sensitive information, addition or modification of data, or Denial of Service (DoS) (NetApp Advisory).

The vulnerability requires local access and can only be exploited when the Pressure Stall Information feature is enabled, which is disabled by default in the Linux kernel (NVD).

The vulnerability was fixed in Linux kernel version 5.17 through a patch that disallows redefining existing PSI triggers. The fix implements changes to prevent trigger redefinition by returning an EBUSY error when attempting to write to a file descriptor with an existing PSI trigger (Kernel Commit).