Directory nlink Overflow in Linux Kernel JFS Implementation

CVE-2025-71292

What is CVE-2025-71292?

A vulnerability in the JFS (Journaled File System) implementation of the Linux kernel could potentially result in an nlink overflow when renaming directories under specific conditions. If the nlink count for a directory reaches the maximum value (-1) and a rename operation occurs on a child directory without moving it from the parent, the process of incrementing and then decrementing the nlink can lead to wraparound, resulting in an incorrect nlink value of 0. This erroneous condition triggers warnings during operations. After addressing this issue with a patch, the system no longer produces warnings, indicating that it has been effectively resolved and basic file system tests show no regressions.

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