[PATCH 1/6 net-next] net: uapi: Add __kernel_sockaddr_unspec for sockaddr of unknown length
From: Kees Cook <kees@kernel.org>
Date: 2025-07-23 23:19:26
Subsystem:
networking [general], networking [sockets], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
Add flexible sockaddr structure to support addresses longer than the
traditional 14-byte struct sockaddr::sa_data limitation. This allows the
network APIs to pass around a pointer to an object that isn't lying to
the compiler about how big it is.
I added this to UAPI in the hopes that it could also be used for any
future "arbitrarily sized" sockaddr needs. But it may be better to
use a different UAPI with an explicit size member:
struct sockaddr_unspec {
u16 sa_data_len;
u16 sa_family;
u8 sa_data[] __counted_by(sa_data_len);
};
Signed-off-by: Kees Cook <kees@kernel.org>
---
include/linux/net.h | 2 ++
include/uapi/linux/socket.h | 15 +++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/include/linux/net.h b/include/linux/net.h
index ec09620f40f7..77de581bdd56 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h@@ -26,6 +26,8 @@ #include <uapi/linux/net.h> +#define sockaddr_unspec __kernel_sockaddr_unspec + struct poll_table_struct; struct pipe_inode_info; struct inode;
diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index d3fcd3b5ec53..2667dd64fd0f 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h@@ -26,6 +26,21 @@ struct __kernel_sockaddr_storage { }; }; +/** + * struct __kernel_sockaddr_unspec - Unspecified size sockaddr for callbacks + * @sa_family: Address family (AF_UNIX, AF_INET, AF_INET6, etc.) + * @sa_data: Flexible array for address data + * + * This structure is designed for callback interfaces where the + * total size is known via the sockaddr_len parameter. Unlike struct + * sockaddr which has a fixed 14-byte sa_data limit, this structure + * can accommodate addresses of any size. + */ +struct __kernel_sockaddr_unspec { + __kernel_sa_family_t sa_family; /* address family, AF_xxx */ + char sa_data[]; /* flexible address data */ +}; + #define SOCK_SNDBUF_LOCK 1 #define SOCK_RCVBUF_LOCK 2
--
2.34.1