From 362b87f5b1c6603b72699e8bb18661ecc4efc0bb Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Fri, 28 Jun 2019 16:40:21 +0200 Subject: [PATCH] netlink: use 48 byte ctx instead of 6 signed longs for callback People are inclined to stuff random things into cb->args[n] because it looks like an array of integers. Sometimes people even put u64s in there with comments noting that a certain member takes up two slots. The horror! Really this should mirror the usage of skb->cb, which are just 48 opaque bytes suitable for casting a struct. Then people can create their usual casting macros for accessing strongly typed members of a struct. As a plus, this also gives us the same amount of space on 32bit and 64bit. Signed-off-by: Jason A. Donenfeld Reviewed-by: Johannes Berg Signed-off-by: David S. Miller --- include/linux/netlink.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 593d1b9c33a8..205fa7b1f07a 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -192,7 +192,14 @@ struct netlink_callback { bool strict_check; u16 answer_flags; unsigned int prev_seq, seq; - long args[6]; + union { + u8 ctx[48]; + + /* args is deprecated. Cast a struct over ctx instead + * for proper type safety. + */ + long args[6]; + }; }; struct netlink_notify { -- 2.34.1