CVE-2026-89702

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/95d064f9828a20ccca5ae90a17be3e2076f25272
• https://git.kernel.org/stable/c/7ff8d6363cffff45654ea85e319f7c0c54226012
• https://git.kernel.org/stable/c/719a10e3f5f868c3c4ac3cf3648c5775d12034bd
• https://git.kernel.org/stable/c/71d068490098b1d23c63b2345e40675d3a1ca763

• ←Previous
• Next→