On Tue, Jul 22, 2025 at 09:58:37AM -0700, Kees Cook wrote: > Add documentation clarifying that ARP and routing UAPI structures are > constrained to IPv4-only usage, making them safe for the coming fixed-size > sockaddr conversion (with the 14-byte struct sockaddr::sa_data). These > are fine as-is, but their use was non-obvious to me, so I figured they > could use a little more documentation: > > - struct arpreq: ARP protocol is IPv4-only by design > - struct rtentry: Legacy IPv4 routing API, IPv6 uses different structures
I'm not sure this second statement is strictly true: https://elixir.bootlin.com/linux/v6.15.7/source/net/appletalk/ddp.c#L918 atrtr_ioctl() -> atrtr_create()-> struct sockaddr_at *ta = (struct sockaddr_at *)&r->rt_dst; where: struct sockaddr_at { __kernel_sa_family_t sat_family; __u8 sat_port; struct atalk_addr sat_addr; char sat_zero[8]; }; This is not an IPv4 address. Maybe this does fit with a 14 byte sockaddr::sa_data, so it is not an issue, but the comment and commit message should be expanded to explain this. And i only looked at the first SIOCADDRT i came across, there are many other protocols using this ioctl. Andrew
