UBUNTU-CVE-2026-23253: Security vulnerability

In the Linux kernel, the following vulnerability has been resolved: media: dvb-core: fix wrong reinitialization of ringbuffer on reopen dvbdvropen() calls dvbringbufferinit() when a new reader opens the DVR device. dvbringbufferinit() calls initwaitqueuehead(), which reinitializes the waitqueue list head to empty. Since dmxdev->dvrbuffer.queue is a shared waitqueue (all opens of the same DVR device share it), this orphans any existing waitqueue entries from iouring poll or epoll, leaving them with stale prev/next pointers while the list head is reset to {self, self}. The waitqueue and spinlock in dvrbuffer are already properly initialized once in dvbdmxdevinit(). The open path only needs to reset the buffer data pointer, size, and read/write positions. Replace the dvbringbufferinit() call in dvbdvropen() with direct assignment of data/size and a call to dvbringbufferreset(), which properly resets pread, pwrite, and error with correct memory ordering without touching the waitqueue or spinlock.