Squashfs Vulnerability in Linux Kernel Affecting Overlayfs Functionality

CVE-2025-40200

What is CVE-2025-40200?

In the Linux kernel, a vulnerability in the Squashfs file system has been identified, which causes a 'WARNING in ovl_copy_up_file' when overlayfs is utilized. This issue occurs due to the underlying Squashfs returning a negative file size, resulting in improper error handling and file operations. To address this, a recent update adds a check for negative file sizes in the squashfs_read_inode() function, returning an EINVAL error when a negative file size is encountered. This fix enhances the stability and reliability of the overlayfs functionality within the Linux kernel.

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