GHSA-VWC6-74MR-XH83
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32In 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": [],
"aliases": [
"CVE-2026-89702"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:57Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: size fh_verify server sockaddr slot by xpt_locallen\n\nThe nfsd_fh_verify and nfsd_fh_verify_err tracepoints declare the\nserver sockaddr slot sized by xpt_remotelen but fill it from\nxpt_local using xpt_locallen:\n\n TP_STRUCT__entry(\n ...\n __sockaddr(server, rqstp-\u003erq_xprt-\u003expt_remotelen)\n ...\n )\n TP_fast_assign(\n ...\n __assign_sockaddr(server, \u0026rqstp-\u003erq_xprt-\u003expt_local,\n rqstp-\u003erq_xprt-\u003expt_locallen);\n ...\n )\n\nWhen xpt_locallen exceeds xpt_remotelen, __assign_sockaddr\u0027s memcpy\nwrites past the reserved ring-buffer slot. In the reverse direction\n(xpt_locallen \u003c xpt_remotelen) the slot is oversized and the\nunwritten tail leaks prior ring-buffer contents to trace consumers.\n\nThe write-past-end case is reachable on NFS/UDP. svc_xprt_set_remote()\nis only called from svc_tcp_accept() (net/sunrpc/svcsock.c) and from\nthe RDMA connect path; svc_create_socket() for UDP calls only\nsvc_xprt_set_local(), so xpt_remotelen stays 0 for the xprt\u0027s\nlifetime. Every fh_verify trace for an NFSv2/v3-over-UDP request\nthen copies 16 or 28 bytes from xpt_local into a zero-byte slot.\n\nThe other NFSD tracepoints that record the server address\n(NFSD_TRACE_PROC_CALL_FIELDS, NFSD_TRACE_PROC_RES_FIELDS,\nSVC_RQST_ENDPOINT_FIELDS) already size the server slot by\nxpt_locallen; nfsd_fh_verify and nfsd_fh_verify_err were the only\nexceptions.\n\nFix by sizing the server slot with xpt_locallen so the declared slot\nmatches the copy length. The client slot and its assignment already\nagree on xpt_remotelen and are left untouched.",
"id": "GHSA-vwc6-74mr-xh83",
"modified": "2026-09-13T09:32:28Z",
"published": "2026-09-11T21:31:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89702"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/719a10e3f5f868c3c4ac3cf3648c5775d12034bd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/71d068490098b1d23c63b2345e40675d3a1ca763"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7ff8d6363cffff45654ea85e319f7c0c54226012"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/95d064f9828a20ccca5ae90a17be3e2076f25272"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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