CVE-2026-74512: audit: fix potential use-after-free in audit_del_rule()

In the Linux kernel, the following vulnerability has been resolved:

audit: fix potential use-after-free in auditdelrule()

auditdelrule() destroys e->rule.exe via auditremovemarkrule() before unlinking the rule from RCU-visible filter lists and waiting for a grace period. Concurrent readers in auditfilter() and auditfilterrules() still dereference e->rule.exe, while the fsnotify mark can be freed on an independent lifetime path. This creates a use-after-free window during rule deletion.

Fix this by unlinking the rule from the RCU-visible lists and invoking synchronizercu() before calling auditremovemarkrule() (and other rule removal helpers). This ensures that all existing RCU readers have exited the critical section before any underlying resources are destroyed.