CVE-2026-19947 Missing kernel object permission check in devmux syscalls allows unprivileged user threads to retarget a device multiplexer

The device multiplexer pseudo-driver in drivers/misc/devmux/devmux.c exposes two system calls, devmuxselectget and devmuxselectset. When CONFIGUSERSPACE is enabled, their user-mode verifiers zvrfydevmuxselectget and zvrfydevmuxselectset forwarded directly to the kernel implementations without...