Re: [PATCH v3 1/9] net: Add struct sockaddr_unspec for sockaddr of unknown length
From: David Laight <hidden>
Date: 2025-10-21 09:26:03
Also in:
bpf, linux-hardening, lkml
On Mon, 20 Oct 2025 14:26:30 -0700 Kees Cook [off-list ref] wrote:
Add flexible sockaddr structure to support addresses longer than the
traditional 14-byte struct sockaddr::sa_data limitation without
requiring the full 128-byte sa_data of struct sockaddr_storage. 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, but must be accompanied
by its actual size as an additional parameter.
It's possible we may way to migrate to including the size with the
struct in the future, e.g.:
struct sockaddr_unspec {
u16 sa_data_len;
u16 sa_family;
u8 sa_data[] __counted_by(sa_data_len);
};One on the historic Unix implementations split the 'sa_family' field into two single byte fields - the second one containing the length. That might work - although care would be needed not to pass a length back to userspace. NetBSD certainly forbid declaring variables of type 'sockaddr storage', the kernel could only use pointers to it. These days that might be enforcable by the compiler. David