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: Jes Sorensen <j...@trained-monkey.org>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Jakub Kicinski <k...@kernel.org>
Cc: linux-hi...@sunsite.dk
Cc: net...@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 net/802/hippi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/802/hippi.c b/net/802/hippi.c
index f80b33a8f7e0..6f71ffc8bdd1 100644
--- a/net/802/hippi.c
+++ b/net/802/hippi.c
@@ -65,7 +65,7 @@ static int hippi_header(struct sk_buff *skb, struct 
net_device *dev,
        hip->le.src_addr_type   = 2;    /* 12 bit SC address */
 
        memcpy(hip->le.src_switch_addr, dev->dev_addr + 3, 3);
-       memset(&hip->le.reserved, 0, 16);
+       memset_startat(&hip->le, 0, reserved);
 
        hip->snap.dsap          = HIPPI_EXTENDED_SAP;
        hip->snap.ssap          = HIPPI_EXTENDED_SAP;
-- 
2.30.2

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