kernel: audit: fix out-of-bounds read in audit_compare_dname_path()

An out of bounds read exists in the linux kernel such that when a watch on dir=/ is combined with an fsnotify event for a single-character name directly under root an out-of-bounds read can occur in auditcomparednamepath...

CVE-2025-39840

The CVE-2025-39840 in the Linux kernel is a fixed out-of-bounds read in audit_compare_dname_path() when a watch on / coincides with a single-character create under / (e.g., /a). The root cause is that parent_len() returns 1 for "/"; audit_compare_dname_path() can set pathlen to 0 and dereference ...