CVE-2026-72467: xprtrdma: Check frwr_wp_create() during connect

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

xprtrdma: Check frwrwpcreate() during connect

frwrwpcreate() creates the singleton Memory Region used to encode padding for Write chunks whose payload length is not XDR-aligned. Its failure paths return a negative errno and leave ep->rewritepadmr set to NULL.

rpcrdmaxprtconnect() currently ignores that return value. If frwrwpcreate() fails after the rest of the connection setup succeeds, xprtrdmaconnectworker() treats the connection attempt as successful and sets XPRTCONNECTED. A later NFS/RDMA read with a non-4-byte-aligned receive page length reaches rpcrdmaencodewritelist(), passes the NULL write-pad MR to encoderdmasegment(), and dereferences it.

This is locally triggerable on an NFS/RDMA client after a connect or reconnect hits a local MR allocation, DMA-map, MR-map, or post-send failure; a remote peer alone cannot force the local MR setup failure.

Check the return value and fail the connect as -ENOTCONN, matching the adjacent setup failures. This keeps XPRTCONNECTED clear and lets the normal reconnect path retry.