nfsd: Fixes for nfsd4_encode_read_plus_data()

stable inclusion
from stable-5.10.11
commit de82ec8e5e8cba33f84ebef26478b636e94a90fb
bugzilla: 47621

--------------------------------

[ Upstream commit 72d78717 ]

Ensure that we encode the data payload + padding, and that we truncate
the preallocated buffer to the actual read size.

Fixes: 528b8493 ("NFSD: Add READ_PLUS data support")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

fs/nfsd/nfs4xdr.c

@@ -4632,6 +4632,7 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
 			    resp->rqstp->rq_vec, read->rd_vlen, maxcount, eof);
 	if (nfserr)
 		return nfserr;
+	xdr_truncate_encode(xdr, starting_len + 16 + xdr_align_size(*maxcount));
 
 	tmp = htonl(NFS4_CONTENT_DATA);
 	write_bytes_to_xdr_buf(xdr->buf, starting_len,      &tmp,   4);
@@ -4639,6 +4640,10 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
 	write_bytes_to_xdr_buf(xdr->buf, starting_len + 4,  &tmp64, 8);
 	tmp = htonl(*maxcount);
 	write_bytes_to_xdr_buf(xdr->buf, starting_len + 12, &tmp,   4);
+
+	tmp = xdr_zero;
+	write_bytes_to_xdr_buf(xdr->buf, starting_len + 16 + *maxcount, &tmp,
+			       xdr_pad_size(*maxcount));
 	return nfs_ok;
 }