Local privilege escalation via nonconsecutive page coalescing

Out-of-bounds physical-memory access in Linux Kernel 6.3-rc1 through 6.3.1 allows local users to gain root privileges. io_sqe_buffer_register treats repeated mappings of one physical page as a contiguous folio because it compares folio identity without verifying page sequence, then records the user-supplied virtual length in one bio_vec. A low-privileged local process can register the crafted fixed buffer and obtain out-of-bounds reads and writes across following physical pages, enabling root takeover.