Gavin Shan

**Name of the Vulnerable Software and Affected Versions** Linux kernel versions prior to 6.6.43 **Description** The Linux kernel has a vulnerability related to the creation of PMD-sized page cache. On ARM64 systems, when the base page size is 64KB, HPAGE PMD ORDER is 13, which cannot be supported by xarray. This results in error messages indicating a problem with the `xas split alloc` function. The issue arises when the size of the PMD-sized page cache exceeds MAX PAGECACHE ORDER. To resolve this, the kernel will skip allocating PMD-sized page cache when its size is larger than MAX PAGECACHE ORDER and fall back to the regular path, where the readahead window is determined by BDI's sysfs file (`read ahead kb`). **Recommendations** To resolve the issue, update the Linux kernel to version 6.6.43 or later. If updating is not possible, consider temporarily disabling the `xas split alloc` function or restricting the use of PMD-sized page cache until a patch is available. Additionally, ensure that BDI's sysfs file (`read ahead kb`) is properly configured to determine the readahead window.