CVE-2026-63949 auxdisplay: line-display: fix OOB read on zero-length message_store()

In the Linux kernel, the following vulnerability has been resolved: auxdisplay: line-display: fix OOB read on zero-length messagestore linedispdisplay unconditionally reads msgcount - 1 before checking whether count is zero, so a write of zero bytes to the message sysfs attribute hits msg-1:...