UBUNTU-CVE-2026-89714: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: NFS: fix delegationhashtable leak when nfs4servercommonsetup() fails nfs4servercommonsetup() allocates server->delegationhashtable first, but server->destroy - the only path that frees the table via nfs4destroyserver() - is not assigned until the very end of the function. If any intermediate step fails (the isdsonlyclient() check, nfs4initsession(), nfs4getrootfh(), or nfsprobeserver()), the function returns with server->destroy still NULL, so the caller's nfsfreeserver() skips the destroy callback and the hash table is leaked (4 KiB per attempt with the default delegation watermark). This is trivially reachable from userspace: every failed NFSv4 mount leaks one allocation. A client that persistently retries a mount that cannot succeed leaks kernel memory without bound. Observed in production where a Longhorn backup poller retried mount.nfs4 against an NFSv3-only server roughly 10 times per second, leaking ~3.4 GiB of unreclaimable slab (kmalloc-rnd-13-4k) per day; the node accumulated 12 GiB of leaked slab before the source was identified via the kmem:kmalloc tracepoint (callsite=nfs4delegationhashalloc). Reproducer: # server exports NFSv3 only (or export path absent for v4) while :; do mount -t nfs4 <server>:/missing /mnt; done # watch SUnreclaim in /proc/meminfo grow 4 KiB per iteration Free the table on the error paths between the allocation and the assignment of server->destroy.