diff options
| author | Alexey Dobriyan <adobriyan@gmail.com> | 2023-09-12 19:22:24 +0300 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2023-09-13 20:09:49 -0700 |
| commit | 32a4ec211d4164e667d9d0b807fadf02053cd2e9 (patch) | |
| tree | 910f19d0b1423e9898ae09b71a3d4e4686685413 /include | |
| parent | 531108ec5b5cd45ec6272a6115e73275baef7d22 (diff) | |
uapi: stddef.h: Fix __DECLARE_FLEX_ARRAY for C++
__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: 3080ea5553cc ("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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/stddef.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h index c027b2070d79..5c6c4269f7ef 100644 --- a/include/uapi/linux/stddef.h +++ b/include/uapi/linux/stddef.h @@ -29,6 +29,11 @@ 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 * @@ -44,6 +49,7 @@ struct { } __empty_ ## NAME; \ TYPE NAME[]; \ } +#endif #ifndef __counted_by #define __counted_by(m) |