CVE-2026-53262 l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()

In the Linux kernel, the following vulnerability has been resolved: l2tp: pppol2tp: hold reference to session in pppol2tpioctl pppol2tpioctl read sock-sk-skuserdata directly without any locks or reference counting. If a controllable sleep was induced during copyfromuser e.g. via a userfaultfd pag...