NFSD: fix dest to src mount in inter-server COPY

commit 614c9750173e412663728215152cc6d12bcb3425 upstream.

A cleanup of the inter SSC copy needs to call fput() of the source
file handle to make sure that file structure is freed as well as
drop the reference on the superblock to unmount the source server.

Fixes: 36e1e5ba90 ("NFSD: Fix use-after-free warning when doing inter-server copy")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfsd/nfs4proc.c

@@ -1299,7 +1299,7 @@ nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct nfsd_file *src,
 			struct nfsd_file *dst)
 {
 	nfs42_ssc_close(src->nf_file);
-	/* 'src' is freed by nfsd4_do_async_copy */
+	fput(src->nf_file);
 	nfsd_file_put(dst);
 	mntput(ss_mnt);
 }