6.6-stable review patch. If anyone has any objections, please let me know.
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From: Dmitry Antipov dmantipov@yandex.ru
[ Upstream commit 4e86f32a13af1970d21be94f659cae56bbe487ee ]
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 lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202311150821.cI4yciFE-lkp@intel.com Signed-off-by: Dmitry Antipov dmantipov@yandex.ru 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 keescook@chromium.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/uapi/linux/stddef.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h index 5c6c4269f7efe..2ec6f35cda32e 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. */