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net: Add struct sockaddr_unsized for sockaddr of unknown length

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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_unsized {
	u16 sa_data_len;
	u16 sa_family;
	u8  sa_data[] __counted_by(sa_data_len);
};

Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20251104002617.2752303-1-kees@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kees Cook
2025-11-03 16:26:09 -08:00
committed by Jakub Kicinski
parent bd0fa86073
commit bf33247a90
1 changed files with 17 additions and 0 deletions
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17
include/linux/socket.h
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@@ -40,6 +40,23 @@ struct sockaddr {
};
};
/**
* struct sockaddr_unsized - 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 or struct
* sockaddr_storage which has a fixed 128-byte sa_data limit, this
* structure can accommodate addresses of any size, but must be used
* carefully.
*/
struct sockaddr_unsized {
__kernel_sa_family_t sa_family; /* address family, AF_xxx */
char sa_data[]; /* flexible address data */
};
struct linger {
int l_onoff; /* Linger active */
int l_linger; /* How long to linger for */