cifs: fix memory leak in SMB2_read

Commit 088aaf17 introduced a leak where
if SMB2_read() returned an error we would return without freeing the
request buffer.

Cc: Stable <stable@vger.kernel.org>
Signed-off-by: NRonnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: NPavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: NSteve French <stfrench@microsoft.com>

fs/cifs/smb2pdu.c

@@ -3466,6 +3466,7 @@ SMB2_read(const unsigned int xid, struct cifs_io_parms *io_parms,
 				    io_parms->tcon->tid, ses->Suid,
 				    io_parms->offset, 0);
 		free_rsp_buf(resp_buftype, rsp_iov.iov_base);
+		cifs_small_buf_release(req);
 		return rc == -ENODATA ? 0 : rc;
 	} else
 		trace_smb3_read_done(xid, req->PersistentFileId,