| Message ID | 20190628144022.31376-1-Jason@zx2c4.com |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | netlink: use 48 byte ctx instead of 6 signed longs for callback | expand |
From: Johannes Berg <johannes@sipsolutions.net> Date: Fri, 28 Jun 2019 16:42:26 +0200 > On Fri, 2019-06-28 at 16:40 +0200, Jason A. Donenfeld wrote: >> 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 <Jason@zx2c4.com> >> Cc: Johannes Berg <johannes@sipsolutions.net> > > Reviewed-by: Johannes Berg <johannes@sipsolutions.net> Applied to net-next.
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 {
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 <Jason@zx2c4.com> Cc: Johannes Berg <johannes@sipsolutions.net> --- include/linux/netlink.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)