Linux CVE-2025-71269

The vulnerability is located in the Btrfs filesystem code within the Linux kernel, specifically in the qgroup (quota group) data reservation handling during inline extent creation fallback scenarios. The Btrfs filesystem uses qgroups to track and limit data usage across subvolumes. When the kernel attempts to create an inline extent (a small file stored directly in metadata) and encounters insufficient space (-ENOSPC), it falls back to a normal copy-on-write allocation path. However, the buggy code in __cow_file_range_inline() unconditionally frees the reserved qgroup data quota even when fallback occurs, meaning the quota is released but the data space is still consumed by the fallback COW operation. This violates the invariant that reserved qgroup quota must match actual usage. The affected products are identified via CPE as cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:* across all affected versions. While no specific CWE is listed in the disclosure, this represents a resource management flaw where quota accounting and actual resource consumption become desynchronized.