From 4e86f32a13af1970d21be94f659cae56bbe487ee Mon Sep 17 00:00:00 2001 From: Dmitry Antipov Date: Mon, 20 Nov 2023 14:05:08 +0300 Subject: uapi: propagate __struct_group() attributes to the container union Recently the kernel test robot has reported an ARM-specific BUILD_BUG_ON() in an old and unmaintained wil6210 wireless driver. The problem comes from the structure packing rules of old ARM ABI ('-mabi=apcs-gnu'). For example, the following structure is packed to 18 bytes instead of 16: struct poorly_packed { unsigned int a; unsigned int b; unsigned short c; union { struct { unsigned short d; unsigned int e; } __attribute__((packed)); struct { unsigned short d; unsigned int e; } __attribute__((packed)) inner; }; } __attribute__((packed)); To fit it into 16 bytes, it's required to add packed attribute to the container union as well: struct poorly_packed { unsigned int a; unsigned int b; unsigned short c; union { struct { unsigned short d; unsigned int e; } __attribute__((packed)); struct { unsigned short d; unsigned int e; } __attribute__((packed)) inner; } __attribute__((packed)); } __attribute__((packed)); Thanks to Andrew Pinski of GCC team for sorting the things out at https://gcc.gnu.org/pipermail/gcc/2023-November/242888.html. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202311150821.cI4yciFE-lkp@intel.com Signed-off-by: Dmitry Antipov Link: https://lore.kernel.org/r/20231120110607.98956-1-dmantipov@yandex.ru Fixes: 50d7bd38c3aa ("stddef: Introduce struct_group() helper macro") Signed-off-by: Kees Cook --- include/uapi/linux/stddef.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h index 5c6c4269f7ef..2ec6f35cda32 100644 --- a/include/uapi/linux/stddef.h +++ b/include/uapi/linux/stddef.h @@ -27,7 +27,7 @@ union { \ struct { MEMBERS } ATTRS; \ struct TAG { MEMBERS } ATTRS NAME; \ - } + } ATTRS #ifdef __cplusplus /* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */ -- cgit v1.2.3