netdev - [PATCH net-next] net: switchdev: add reminder near struct switchdev_notifier_fdb

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Date:   Tue, 28 Jun 2022 13:08:31 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Ido Schimmel <idosch@...dia.com>
Subject: [PATCH net-next] net: switchdev: add reminder near struct switchdev_notifier_fdb_info

br_switchdev_fdb_notify() creates an on-stack FDB info variable, and
initializes it member by member. As such, newly added fields which are
not initialized by br_switchdev_fdb_notify() will contain junk bytes
from the stack.

Other uses of struct switchdev_notifier_fdb_info have a struct
initializer which should put zeroes in the uninitialized fields.

Add a reminder above the structure for future developers. Recently
discussed during review.

Link: https://patchwork.kernel.org/project/netdevbpf/patch/20220524152144.40527-2-schultz.hans+netdev@gmail.com/#24877698
Link: https://patchwork.kernel.org/project/netdevbpf/patch/20220524152144.40527-3-schultz.hans+netdev@gmail.com/#24912269
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 include/net/switchdev.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/net/switchdev.h b/include/net/switchdev.h
index aa0171d5786d..7dcdc97c0bc3 100644
--- a/include/net/switchdev.h
+++ b/include/net/switchdev.h
@@ -239,6 +239,9 @@ struct switchdev_notifier_info {
 	const void *ctx;
 };
 
+/* Remember to update br_switchdev_fdb_populate() when adding
+ * new members to this structure
+ */
 struct switchdev_notifier_fdb_info {
 	struct switchdev_notifier_info info; /* must be first */
 	const unsigned char *addr;
-- 
2.25.1