mirror of
https://git.proxmox.com/git/mirror_ubuntu-kernels.git
synced 2025-12-23 15:20:19 +00:00
32a4ec211d
__DECLARE_FLEX_ARRAY(T, member) macro expands to
struct {
struct {} __empty_member;
T member[];
};
which is subtly wrong in C++ because sizeof(struct{}) is 1 not 0,
changing UAPI structures layouts.
This can be fixed by expanding to
T member[];
Now g++ doesn't like "T member[]" either, throwing errors on
the following code:
struct S {
union {
T1 member1[];
T2 member2[];
};
};
or
struct S {
T member[];
};
Use "T member[0];" which seems to work and does the right thing wrt
structure layout.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Fixes: 3080ea5553 ("stddef: Introduce DECLARE_FLEX_ARRAY() helper")
Link: https://lore.kernel.org/r/97242381-f1ec-4a4a-9472-1a464f575657@p183
Signed-off-by: Kees Cook <keescook@chromium.org>
59 lines
1.8 KiB
C
59 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
|
|
#ifndef _UAPI_LINUX_STDDEF_H
|
|
#define _UAPI_LINUX_STDDEF_H
|
|
|
|
#include <linux/compiler_types.h>
|
|
|
|
#ifndef __always_inline
|
|
#define __always_inline inline
|
|
#endif
|
|
|
|
/**
|
|
* __struct_group() - Create a mirrored named and anonyomous struct
|
|
*
|
|
* @TAG: The tag name for the named sub-struct (usually empty)
|
|
* @NAME: The identifier name of the mirrored sub-struct
|
|
* @ATTRS: Any struct attributes (usually empty)
|
|
* @MEMBERS: The member declarations for the mirrored structs
|
|
*
|
|
* Used to create an anonymous union of two structs with identical layout
|
|
* and size: one anonymous and one named. The former's members can be used
|
|
* normally without sub-struct naming, and the latter can be used to
|
|
* reason about the start, end, and size of the group of struct members.
|
|
* The named struct can also be explicitly tagged for layer reuse, as well
|
|
* as both having struct attributes appended.
|
|
*/
|
|
#define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
|
|
union { \
|
|
struct { MEMBERS } ATTRS; \
|
|
struct TAG { MEMBERS } ATTRS NAME; \
|
|
}
|
|
|
|
#ifdef __cplusplus
|
|
/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
|
|
#define __DECLARE_FLEX_ARRAY(T, member) \
|
|
T member[0]
|
|
#else
|
|
/**
|
|
* __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
|
|
*
|
|
* @TYPE: The type of each flexible array element
|
|
* @NAME: The name of the flexible array member
|
|
*
|
|
* In order to have a flexible array member in a union or alone in a
|
|
* struct, it needs to be wrapped in an anonymous struct with at least 1
|
|
* named member, but that member can be empty.
|
|
*/
|
|
#define __DECLARE_FLEX_ARRAY(TYPE, NAME) \
|
|
struct { \
|
|
struct { } __empty_ ## NAME; \
|
|
TYPE NAME[]; \
|
|
}
|
|
#endif
|
|
|
|
#ifndef __counted_by
|
|
#define __counted_by(m)
|
|
#endif
|
|
|
|
#endif /* _UAPI_LINUX_STDDEF_H */
|