Linux Kernel Ext4 Bigalloc and Inline Data Delayed Allocation Vulnerability

A vulnerability in the Linux kernel's ext4 file system can lead to several issues, including invalid extent status cache content, incorrect reserved cluster counts, kernel memory leaks, and potential kernel panics. This vulnerability arises when files with inline data are converted to extent mapping on a file system created with both the bigalloc and inline options. The problem occurs because the current allocation process improperly searches a non-existent extent tree for previously allocated clusters, leading to the caching of invalid data. This issue can be exploited during the conversion of inline data files to extent-mapped files on bigalloc-enabled file systems.

Impact

Exploitation of this vulnerability can cause kernel memory leaks and potentially lead to a kernel panic, disrupting system operations.

Reproduction

To reproduce this vulnerability, create a file system with both the bigalloc and inline options enabled. Then, convert a file with inline data to extent mapping. During this conversion, the file system's delayed allocation process will incorrectly search for allocated clusters in a non-existent extent tree, causing the issues associated with this vulnerability.

Remediation

Users can upgrade to the patched version of the Linux kernel available in the Linux Kernel Git Repository under the stable branch. Instructions for downloading this version are available on the repository's website.