CVE-2026-89702

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

nfsd: size fh_verify server sockaddr slot by xpt_locallen

The nfsd_fh_verify and nfsd_fh_verify_err tracepoints declare the
server sockaddr slot sized by xpt_remotelen but fill it from
xpt_local using xpt_locallen:

    TP_STRUCT__entry(
            ...
            __sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
            ...
    )
    TP_fast_assign(
            ...
            __assign_sockaddr(server, &rqstp->rq_xprt->xpt_local,
                              rqstp->rq_xprt->xpt_locallen);
            ...
    )

When xpt_locallen exceeds xpt_remotelen, __assign_sockaddr's memcpy
writes past the reserved ring-buffer slot. In the reverse direction
(xpt_locallen < xpt_remotelen) the slot is oversized and the
unwritten tail leaks prior ring-buffer contents to trace consumers.

The write-past-end case is reachable on NFS/UDP. svc_xprt_set_remote()
is only called from svc_tcp_accept() (net/sunrpc/svcsock.c) and from
the RDMA connect path; svc_create_socket() for UDP calls only
svc_xprt_set_local(), so xpt_remotelen stays 0 for the xprt's
lifetime. Every fh_verify trace for an NFSv2/v3-over-UDP request
then copies 16 or 28 bytes from xpt_local into a zero-byte slot.

The other NFSD tracepoints that record the server address
(NFSD_TRACE_PROC_CALL_FIELDS, NFSD_TRACE_PROC_RES_FIELDS,
SVC_RQST_ENDPOINT_FIELDS) already size the server slot by
xpt_locallen; nfsd_fh_verify and nfsd_fh_verify_err were the only
exceptions.

Fix by sizing the server slot with xpt_locallen so the declared slot
matches the copy length. The client slot and its assignment already
agree on xpt_remotelen and are left untouched.