Re: [PATCH v2][next] Bluetooth: Avoid a couple dozen -Wflex-array-member-not-at-end warnings

Gustavo A. R. Silva
2025-09-25T12:37:55Z

Hi all,

Friendly ping: who can take this, please? :)

Thanks!
-Gustavo

On 9/9/25 14:13, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
>
> Use the __struct_group() helper to fix 31 instances of the following
> type of warnings:
>
> 30 net/bluetooth/mgmt_config.c:16:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 1 net/bluetooth/mgmt_config.c:22:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes in v2:
> - Use __struct_group() instead of TRAILING_OVERLAP().
>
> v1:
> - Link: https://lore.kernel.org/linux-hardening/aLSCu8U62Hve7Dau@kspp/
>
> include/net/bluetooth/mgmt.h | 9 +++++++--
> net/bluetooth/mgmt_config.c | 4 ++--
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.h
> index 3575cd16049a..74edea06985b 100644
> --- a/include/net/bluetooth/mgmt.h
> +++ b/include/net/bluetooth/mgmt.h
> @@ -53,10 +53,15 @@ struct mgmt_hdr {
> } __packed;
>
> struct mgmt_tlv {
> - __le16 type;
> - __u8 length;
> + /* New members MUST be added within the __struct_group() macro below. */
> + __struct_group(mgmt_tlv_hdr, __hdr, __packed,
> + __le16 type;
> + __u8 length;
> + );
> __u8 value[];
> } __packed;
> +static_assert(offsetof(struct mgmt_tlv, value) == sizeof(struct mgmt_tlv_hdr),
> + "struct member likely outside of __struct_group()");
>
> struct mgmt_addr_info {
> bdaddr_t bdaddr;
> diff --git a/net/bluetooth/mgmt_config.c b/net/bluetooth/mgmt_config.c
> index 6ef701c27da4..c4063d200c0a 100644
> --- a/net/bluetooth/mgmt_config.c
> +++ b/net/bluetooth/mgmt_config.c
> @@ -13,13 +13,13 @@
>
> #define HDEV_PARAM_U16(_param_name_) \
> struct {\
> - struct mgmt_tlv entry; \
> + struct mgmt_tlv_hdr entry; \
> __le16 value; \
> } __packed _param_name_
>
> #define HDEV_PARAM_U8(_param_name_) \
> struct {\
> - struct mgmt_tlv entry; \
> + struct mgmt_tlv_hdr entry; \
> __u8 value; \
> } __packed _param_name_
>