UBUNTU-CVE-2026-90102: High severity ubuntu/linux-aws vulnerability

In the Linux kernel, the following vulnerability has been resolved: NFSv4/pnfs: key the data server cache on the NFS version nfs4pnfsdsadd() keys the per-net data server cache on the multipath address set alone, and struct nfs4pnfsds records no version. That suffices for the files layout driver, which always connects with version 4, but flexfiles takes its version tuple from GETDEVICEINFO per device, and one address can legitimately serve both NFSv3 and NFSv4. Two deviceids on one address with different dsversions[0].version therefore share a single nfs4pnfsds, and whichever mirror connects first pins dsclp to its own version. The other one is handed that client anyway, so it selects rpccallops for a version the connection does not speak, and the mismatched sequence-slot handling dereferences NULL. Add the version to the cache key so the two cannot alias, giving each version its own nfs4pnfsds and connection while both mirrors stay usable. Only the major version is compared, since that is what selects rpccallops and rpcops; v4.0 and v4.1 keep sharing a client. The files layout driver passes the 4 it already hardcodes at connect time.