There are cases in networking (e.g. wireguard, sctp) where a union is used to provide coverage for either IPv4 or IPv6 network addresses, and they include an embedded "struct sockaddr" as well (for "sa_family" and raw "sa_data" access). The current struct sockaddr contains a flexible array, which means these unions should not be further embedded in other structs because they do not technically have a fixed size (and are generating warnings for the coming -Wflexible-array-not-at-end flag addition). But the future changes to make struct sockaddr a fixed size (i.e. with a 14 byte sa_data member) make the "sa_data" uses with an IPv6 address a potential place for the compiler to get upset about object size mismatches. Therefore, we need a sockaddr that cleanly provides both an sa_family member and an appropriately fixed-sized sa_data member that does not bloat member usage via the potential alternative of sockaddr_storage to cover both IPv4 and IPv6, to avoid unseemly churn in the affected code bases. Introduce sockaddr_inet as a unified structure for holding both IPv4 and IPv6 addresses (i.e. large enough to accommodate sockaddr_in6). The structure is defined in linux/in6.h since its max size is sized based on sockaddr_in6 and provides a more specific alternative to the generic sockaddr_storage for IPv4 with IPv6 address family handling. The "sa_family" member doesn't use the sa_family_t type to avoid needing layer violating header inclusions. Signed-off-by: Kees Cook --- include/linux/in6.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/in6.h b/include/linux/in6.h index 0777a21cbf86..403f926d33d8 100644 --- a/include/linux/in6.h +++ b/include/linux/in6.h @@ -18,6 +18,13 @@ #include +/* Large enough to hold both sockaddr_in and sockaddr_in6. */ +struct sockaddr_inet { + unsigned short sa_family; + char sa_data[sizeof(struct sockaddr_in6) - + sizeof(unsigned short)]; +}; + /* IPv6 Wildcard Address (::) and Loopback Address (::1) defined in RFC2553 * NOTE: Be aware the IN6ADDR_* constants and in6addr_* externals are defined * in network byte order, not in host byte order as are the IPv4 equivalents -- 2.34.1