CVE-2026-52908

In the Linux kernel, the following vulnerability has been resolved:

RDMA: During reregmr ensure that REREGACCESS is compatible

If IBMRREREGACCESS changes from RO to RW then the umem has to be re-evaluated to ensure it is properly pinned as RW. Since the umem is hidden inside each driver's mr struct add a ibumemcheckrereg() function that each driver has to call before processing IBMRREREG_ACCESS.

mlx4 has to retain its duplicate ibaccesswritable check because it implements IBMRREREGACCESS | IBMRREREGTRANS by changing both items in place sequentially while the MR is live, so it will continue to not support this combination.