CVE-2026-52930 ipc/shm: serialize orphan cleanup with shm_nattch updates

In the Linux kernel, the following vulnerability has been resolved: ipc/shm: serialize orphan cleanup with shmnattch updates shmdestroyorphaned walks the shm idr under shmidsns.rwsem, but that does not serialize all fields tested by shmmaydestroy. In particular, shmnattch is updated while holding...