CVE-2022-4379: 
Linux Kernel vulnerability analysis and mitigation

A use-after-free vulnerability was discovered in _nfs42ssc_open() function in fs/nfs/nfs4file.c in the Linux kernel through version 6.1. The vulnerability was discovered in December 2022 and assigned CVE-2022-4379. The issue affects the NFSv4.2 inter server to server copy implementation (NVD, OSS-SEC).

The vulnerability is caused by dereferencing a vfsmount which is freed but still remains on the delayed unmount list. This occurs when nfs42sscopen returns an error when called in nfsd4doasync_copy. The bug can be triggered by two consecutive inter-server-side copies if the first one encounters an error (OSS-SEC). The vulnerability has been assigned a CVSS v3.1 base score of 7.5 (High) (NetApp).

When successfully exploited, this vulnerability allows an attacker to conduct a remote denial of service attack. The issue affects the system's stability and availability (NVD, NetApp).

The issue has been fixed in the Linux kernel through a patch submitted by Dai Ngo. The fix involves removing nfsd4intersscconnect() and leaving the vfsmount for the laundromat to unmount when idle time expires (OSS-SEC). Various Linux distributions have released updates to address this vulnerability, including Fedora and Ubuntu (Fedora).