net: 802: Use memset_startat() to clear struct fields

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.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/802/hippi.c b/net/802/hippi.c
index 887e73d520e4977fcb9830cad1933a2b55d9539b..1997b7dd265e3bf364de59f4ff0a1da582f298ef 100644 (file)
--- 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;