[PATCH v2 42/63] net: dccp: Use memset_startat() for TP zeroing

[Kees Cook]

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Use memset_startat() so memset() doesn't get confused about writing
beyond the destination member that is intended to be the starting point
of zeroing through the end of the struct.

Cc: "David S. Miller" <da...@davemloft.net>
Cc: Jakub Kicinski <k...@kernel.org>
Cc: d...@vger.kernel.org
Cc: net...@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 net/dccp/trace.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/dccp/trace.h b/net/dccp/trace.h
index 5062421beee9..5a43b3508c7f 100644
--- a/net/dccp/trace.h
+++ b/net/dccp/trace.h
@@ -60,9 +60,7 @@ TRACE_EVENT(dccp_probe,
                        __entry->tx_t_ipi = hc->tx_t_ipi;
                } else {
                        __entry->tx_s = 0;
-                       memset(&__entry->tx_rtt, 0, (void *)&__entry->tx_t_ipi -
-                              (void *)&__entry->tx_rtt +
-                              sizeof(__entry->tx_t_ipi));
+                       memset_startat(__entry, 0, tx_rtt);
                }
        ),
 
-- 
2.30.2