The BOTH_TIME_SET branch calls fh_verify() early so setattr_prepare()
can inspect the dentry. This causes nfsd_setattr() to skip
fh_want_write(), so notify_change() runs without a mount write
reference.

Add the missing fh_want_write() call after the early fh_verify().

Fixes: cc265089ce1b ("nfsd: Disable NFSv2 timestamp workaround for NFSv3+")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/nfsproc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 8873033d1e82..a73d5c259cd9 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -82,6 +82,7 @@ nfsd_proc_setattr(struct svc_rqst *rqstp)
 		.na_iattr	= iap,
 	};
 	struct svc_fh *fhp;
+	int hosterr;
 
 	dprintk("nfsd: SETATTR  %s, valid=%x, size=%ld\n",
 		SVCFH_fmt(&argp->fh),
@@ -117,6 +118,12 @@ nfsd_proc_setattr(struct svc_rqst *rqstp)
 		if (resp->status != nfs_ok)
 			goto out;
 
+		hosterr = fh_want_write(fhp);
+		if (hosterr) {
+			resp->status = nfserrno(hosterr);
+			goto out;
+		}
+
 		if (delta < 0)
 			delta = -delta;
 		if (delta < MAX_TOUCH_TIME_ERROR &&

-- 
2.54.0