CVE-2021-47166: 
Linux Kernel vulnerability analysis and mitigation

A vulnerability was found in the NFS module in the Linux kernel where a memory corruption occurred in pg_bytes_written in the nfs_do_recoalesce() function. The value was updated before successfully flushing requests, potentially leading to incorrect accounting of written bytes (Red Hat Portal).

The vulnerability stems from a timing issue in the NFS module's page I/O handling where the value of mirror->pg_bytes_written was being updated before confirming the successful flush of requests. The issue was introduced in commit a7d42ddb3099 ("nfs: add mirroring support to pgio layer") and was fixed by ensuring that the value is only updated after a successful attempt to flush out the requests on the list (Kernel Git). The vulnerability has been assigned a CVSS v3.1 base score of 5.5 (Moderate) with vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (Red Hat Portal).

The vulnerability could lead to incorrect accounting of written bytes in NFS operations, potentially affecting system stability and data consistency. The impact is primarily focused on availability, with no direct effect on confidentiality or integrity of the system (Red Hat Portal).

The vulnerability requires local access with low privileges and no user interaction. The attack complexity is considered low, making it relatively straightforward to exploit if an attacker has the necessary local access (Red Hat Portal).

Red Hat recommends updating the affected package as soon as possible. No practical mitigation has been identified as an alternative to updating (Red Hat Portal).