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

Gustavo A. R. Silva
2025-09-09T12:13:43Z

-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_

--
2.43.0