Linux Kernel NFSv4 Dentry Handling Vulnerability

A vulnerability in the Linux kernel's NFS implementation can lead to a null pointer dereference when automounting NFSv4 referrals. This occurs because the path's dentry may become a negative dentry, causing the NFS server structure to be incorrectly derived. The issue has been fixed by properly sourcing the NFS server information from the dentry's superblock.

Impact

The vulnerability can cause a null pointer dereference, leading to a system crash.

Reproduction

To reproduce this vulnerability, mount an NFSv4 referral that results in a negative dentry. This will trigger the incorrect handling in the nfs_d_automount function, causing a null pointer dereference.

Remediation

Users can upgrade to the latest version of the Linux kernel where this vulnerability has been addressed.