On Fri, Aug 14, 2020 at 6:20 AM Alexander Potapenko [off-list ref] wrote:

On Fri, Aug 14, 2020, 13:04 Marc Kleine-Budde [off-list ref] wrote:

quoted

From: Eric Dumazet <edumazet@google.com>

quoted

 net/can/j1939/socket.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 78ff9b3f1d40..b634b680177f 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c

@@ -553,6 +553,11 @@ static int j1939_sk_connect(struct socket *sock, struct sockaddr *uaddr,
 static void j1939_sk_sock2sockaddr_can(struct sockaddr_can *addr,
                                       const struct j1939_sock *jsk, int peer)
 {
+       /* There are two holes (2 bytes and 3 bytes) to clear to avoid
+        * leaking kernel information to user space.
+        */

Do we want to keep these "2 bytes and 3 bytes' in sync with the struct layout in the future? Maybe it's not worth it to mention the exact sizes?

struct is uapi, you will have a hard time trying to use these holes,
since old kernels were sending crap/garbage/passwords ;)