UBUNTU-CVE-2026-98361: High severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: Restore HMMPFNWRITE check in ODP write paths Commit 0b261d7c1cd3 ("RDMA/rxe: Break endless pagefault loop for RO pages") dropped the access permission test from rxecheckpagefault() and left only HMMPFNVALID. A page faulted in read-only, for example a page-cache folio behind a PROTREAD file mapping, then satisfies the check and ODP write operations (RDMA WRITE, RDMA READ response, SEND payload, atomics) modify it through kmap without ever breaking CoW. An unprivileged user can register an ODP MR over such a mapping and have incoming RDMA traffic overwrite the page cache of a file it only holds ORDONLY, including /etc/passwd or setuid binaries. This is the same primitive class as Dirty COW and CVE-2022-2590. mlx5 has the missing invariant: its ODP path sets the device write bit only for pfns that carry HMMPFNWRITE. Restore it in rxe by requiring HMMPFNWRITE in rxecheckpagefault() for every operation except RXEPAGEFAULTRDONLY. A write to a non-writable VMA now fails the one fault attempt with -EPERM from hmmvmafault() instead of re-faulting forever. For a writable VMA the fault breaks CoW and the write lands in the private page. Keep pmem flushes on the read-only check. archwbcachepmem() never modifies memory, and the FLUSH access bits do not make the umem writable, so classifying flushes as writes would make every flush against a flush-only MR fail.