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() to clear everything after the dst_entry member of
struct rt6_info.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Hideaki YOSHIFUJI <redacted>
Cc: David Ahern <dsahern@kernel.org>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <redacted>
---
 net/ipv6/route.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 6cf4bb89ca69..bd0ab3e436e7 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c

@@ -327,9 +327,7 @@ static const struct rt6_info ip6_blk_hole_entry_template = {
 
 static void rt6_info_init(struct rt6_info *rt)
 {
-	struct dst_entry *dst = &rt->dst;
-
-	memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
+	memset_after(rt, 0, dst);
 	INIT_LIST_HEAD(&rt->rt6i_uncached);
 }
 

-- 
2.30.2