CVE-2026-89714

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

NFS: fix delegation hash table leak when nfs4 server common setup() fails

nfs4 server common setup() allocates server->delegation hash table first, but server->destroy - the only path that frees the table via nfs4 destroy server() - is not assigned until the very end of the function. If any intermediate step fails (the is ds only client() check, nfs4 init session(), nfs4 get rootfh(), or nfs probe server()), the function returns with server->destroy still NULL, so the caller's nfs free server() 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 (call site=nfs4 delegation hash alloc).

Reproducer:

while :; do mount -t nfs4 :/missing /mnt; done

Free the table on the error paths between the allocation and the assignment of server->destroy.