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From:   Kees Cook <keescook@chromium.org>
To:     linux-kernel@vger.kernel.org
Cc:     Kees Cook <keescook@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, dccp@vger.kernel.org,
        netdev@vger.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-wireless@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-staging@lists.linux.dev, linux-block@vger.kernel.org,
        linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-hardening@vger.kernel.org
Subject: [PATCH v2 42/63] net: dccp: Use memset_startat() for TP zeroing
Date:   Tue, 17 Aug 2021 23:05:12 -0700
Message-Id: <20210818060533.3569517-43-keescook@chromium.org>
In-Reply-To: <20210818060533.3569517-1-keescook@chromium.org>
References: <20210818060533.3569517-1-keescook@chromium.org>
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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" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: dccp@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@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