CVE-2026-9728: Time-of-check Time-of-use (TOCTOU) Race Condition

The userspace syscall verifier zvrfymboxsend in drivers/mbox/mboxhandlers.c validated the nested msg-data/msg-size fields by reading them directly out of live userspace memory, and then forwarded the original, still-mutable userspace struct mboxmsg pointer to zimplmboxsend and the underlying...