FAILED: patch "[PATCH] nfsd: size fh_verify server sockaddr slot by xpt_locallen" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 71d068490098b1d23c63b2345e40675d3a1ca763
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090324-repaint-carpenter-eb61@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 71d068490098b1d23c63b2345e40675d3a1ca763 Mon Sep 17 00:00:00 2001
From: Chris Mason <[email protected]>
Date: Sun, 31 May 2026 08:06:58 -0400
Subject: [PATCH] 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.

index 830d9ceb4fe3..33953d38314e 100644
@@ -271,7 +271,7 @@ TRACE_EVENT_CONDITION(nfsd_fh_verify,
 	TP_CONDITION(rqstp != NULL),
 	TP_STRUCT__entry(
 		__field(unsigned int, netns_ino)
-		__sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
+		__sockaddr(server, rqstp->rq_xprt->xpt_locallen)
 		__sockaddr(client, rqstp->rq_xprt->xpt_remotelen)
 		__field(u32, xid)
 		__field(u32, fh_hash)

@@ -310,7 +310,7 @@ TRACE_EVENT_CONDITION(nfsd_fh_verify_err,
 	TP_CONDITION(rqstp != NULL && error),
 	TP_STRUCT__entry(
 		__field(unsigned int, netns_ino)
-		__sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
+		__sockaddr(server, rqstp->rq_xprt->xpt_locallen)
 		__sockaddr(client, rqstp->rq_xprt->xpt_remotelen)
 		__field(u32, xid)
 		__field(u32, fh_hash)

From: Chris Mason <[email protected]>

[ Upstream commit 71d068490098b1d23c63b2345e40675d3a1ca763 ]

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.

---
 fs/nfsd/trace.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index d7ed49eef5911..6e57a9dba1a59 100644
@@ -201,7 +201,7 @@ TRACE_EVENT(nfsd_fh_verify,
 	TP_ARGS(rqstp, fhp, type, access),
 	TP_STRUCT__entry(
 		__field(unsigned int, netns_ino)
-		__sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
+		__sockaddr(server, rqstp->rq_xprt->xpt_locallen)
 		__sockaddr(client, rqstp->rq_xprt->xpt_remotelen)
 		__field(u32, xid)
 		__field(u32, fh_hash)

@@ -240,7 +240,7 @@ TRACE_EVENT_CONDITION(nfsd_fh_verify_err,
 	TP_CONDITION(error),
 	TP_STRUCT__entry(
 		__field(unsigned int, netns_ino)
-		__sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
+		__sockaddr(server, rqstp->rq_xprt->xpt_locallen)
 		__sockaddr(client, rqstp->rq_xprt->xpt_remotelen)
 		__field(u32, xid)
 		__field(u32, fh_hash)

2.53.0