RE: [PATCH v2 net-next 1/2] net: dsa: lan9303: Add port_fast_age and port_fdb_dump methods

[David Laight]

From: Egil Hjelmeland
> Sent: 19 October 2017 17:53
...
> >> IMHO it is best to define a struct for the 'ctx and then do:
> >>     ..., void *v_ctx)
> >> {
> >>     foo_ctx *ctx = v_ctx;
> >>     int port = ctx->port;
> >>
> >> That stops anyone having to double-check that the *(int *)
> >> is operating on a pointer to an integer of the correct size.
> >>
> >
> > Does casting to a struct pointer require less manual double-check than
> > to a int-pointer? In neither cases the compiler can protect us, IFAIK.
> > But on the other hand, a the text "foo_ctx" can searched in the editor.
> > So in that respect it can somewhat aid to the double-checking.
> >
> > So I can do that.
> >
> >
> 
> I understand now that the caller side (lan9303_port_fast_age) is
> vulnerable. Say somebody has the idea to change the "port" param
> of .port_fast_age from int to u8, then my code is a trap.

Worse, change it to a long and it will work on everything except
64bit big-endian systems.

	David