linux-hardening - [PATCH 41/64] net: dccp: Use memset

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Message-Id: <20210727205855.411487-42-keescook@chromium.org>
Date:   Tue, 27 Jul 2021 13:58:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH 41/64] net: dccp: Use memset_after() for TP zeroing

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

Use memset_after() 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.

Signed-off-by: Kees Cook <keescook@...omium.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..3c2594da49fc 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_after(__entry, 0, tx_s);
 		}
 	),
 
-- 
2.30.2