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* [PATCH][next] Bluetooth: Avoid a couple dozen -Wflex-array-member-not-at-end warnings
@ 2025-08-31 17:13 Gustavo A. R. Silva
  2025-08-31 17:51 ` [next] " bluez.test.bot
  2025-08-31 18:02 ` [PATCH][next] " Gustavo A. R. Silva
  0 siblings, 2 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2025-08-31 17:13 UTC (permalink / raw)
  To: Marcel Holtmann, Johan Hedberg, Luiz Augusto von Dentz
  Cc: linux-bluetooth, linux-kernel, Gustavo A. R. Silva,
	linux-hardening

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the new TRAILING_OVERLAP() 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]

This helper creates a union between a flexible-array member (FAM)
and a set of members that would otherwise follow it. This overlays
the trailing members onto the FAM while preserving the original
memory layout.

Also, as the structs turn into unions, both members `entry` and
`value` cannot be statically initialized at once. Create another
macro to initialize everything after the declaration of `rp`.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 net/bluetooth/mgmt_config.c | 97 +++++++++++++++++++------------------
 1 file changed, 51 insertions(+), 46 deletions(-)

diff --git a/net/bluetooth/mgmt_config.c b/net/bluetooth/mgmt_config.c
index 6ef701c27da4..829c9cfcea7d 100644
--- a/net/bluetooth/mgmt_config.c
+++ b/net/bluetooth/mgmt_config.c
@@ -12,35 +12,71 @@
 #include "mgmt_config.h"
 
 #define HDEV_PARAM_U16(_param_name_) \
-	struct {\
-		struct mgmt_tlv entry; \
+	TRAILING_OVERLAP(struct mgmt_tlv, entry, value, \
 		__le16 value; \
-	} __packed _param_name_
+	) __packed _param_name_
 
 #define HDEV_PARAM_U8(_param_name_) \
-	struct {\
-		struct mgmt_tlv entry; \
+	TRAILING_OVERLAP(struct mgmt_tlv, entry, value, \
 		__u8 value; \
-	} __packed _param_name_
+	) __packed _param_name_
 
 #define TLV_SET_U16(_param_code_, _param_name_) \
 	{ \
-		{ cpu_to_le16(_param_code_), sizeof(__u16) }, \
-		cpu_to_le16(hdev->_param_name_) \
+		rp._param_name_.entry.type = cpu_to_le16(_param_code_); \
+		rp._param_name_.entry.length = sizeof(__u16); \
+		rp._param_name_.value = cpu_to_le16(hdev->_param_name_); \
 	}
 
 #define TLV_SET_U8(_param_code_, _param_name_) \
 	{ \
-		{ cpu_to_le16(_param_code_), sizeof(__u8) }, \
-		hdev->_param_name_ \
+		rp._param_name_.entry.type = cpu_to_le16(_param_code_); \
+		rp._param_name_.entry.length = sizeof(__u8); \
+		rp._param_name_.value = hdev->_param_name_; \
 	}
 
 #define TLV_SET_U16_JIFFIES_TO_MSECS(_param_code_, _param_name_) \
 	{ \
-		{ cpu_to_le16(_param_code_), sizeof(__u16) }, \
-		cpu_to_le16(jiffies_to_msecs(hdev->_param_name_)) \
+		rp._param_name_.entry.type = cpu_to_le16(_param_code_); \
+		rp._param_name_.entry.length = sizeof(__u16); \
+		rp._param_name_.value = cpu_to_le16(jiffies_to_msecs(hdev->_param_name_)); \
 	}
 
+#define TLV_SET_ALL() \
+{ \
+	TLV_SET_U16(0x0000, def_page_scan_type); \
+	TLV_SET_U16(0x0001, def_page_scan_int); \
+	TLV_SET_U16(0x0002, def_page_scan_window); \
+	TLV_SET_U16(0x0003, def_inq_scan_type);  \
+	TLV_SET_U16(0x0004, def_inq_scan_int); \
+	TLV_SET_U16(0x0005, def_inq_scan_window); \
+	TLV_SET_U16(0x0006, def_br_lsto); \
+	TLV_SET_U16(0x0007, def_page_timeout); \
+	TLV_SET_U16(0x0008, sniff_min_interval); \
+	TLV_SET_U16(0x0009, sniff_max_interval); \
+	TLV_SET_U16(0x000a, le_adv_min_interval); \
+	TLV_SET_U16(0x000b, le_adv_max_interval); \
+	TLV_SET_U16(0x000c, def_multi_adv_rotation_duration); \
+	TLV_SET_U16(0x000d, le_scan_interval); \
+	TLV_SET_U16(0x000e, le_scan_window); \
+	TLV_SET_U16(0x000f, le_scan_int_suspend); \
+	TLV_SET_U16(0x0010, le_scan_window_suspend); \
+	TLV_SET_U16(0x0011, le_scan_int_discovery); \
+	TLV_SET_U16(0x0012, le_scan_window_discovery); \
+	TLV_SET_U16(0x0013, le_scan_int_adv_monitor); \
+	TLV_SET_U16(0x0014, le_scan_window_adv_monitor); \
+	TLV_SET_U16(0x0015, le_scan_int_connect); \
+	TLV_SET_U16(0x0016, le_scan_window_connect); \
+	TLV_SET_U16(0x0017, le_conn_min_interval); \
+	TLV_SET_U16(0x0018, le_conn_max_interval); \
+	TLV_SET_U16(0x0019, le_conn_latency); \
+	TLV_SET_U16(0x001a, le_supv_timeout); \
+	TLV_SET_U16_JIFFIES_TO_MSECS(0x001b, def_le_autoconnect_timeout); \
+	TLV_SET_U16(0x001d, advmon_allowlist_duration); \
+	TLV_SET_U16(0x001e, advmon_no_filter_duration); \
+	TLV_SET_U8(0x001f, enable_advmon_interleave_scan); \
+}
+
 int read_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
 			   u16 data_len)
 {
@@ -78,40 +114,9 @@ int read_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
 		HDEV_PARAM_U16(advmon_allowlist_duration);
 		HDEV_PARAM_U16(advmon_no_filter_duration);
 		HDEV_PARAM_U8(enable_advmon_interleave_scan);
-	} __packed rp = {
-		TLV_SET_U16(0x0000, def_page_scan_type),
-		TLV_SET_U16(0x0001, def_page_scan_int),
-		TLV_SET_U16(0x0002, def_page_scan_window),
-		TLV_SET_U16(0x0003, def_inq_scan_type),
-		TLV_SET_U16(0x0004, def_inq_scan_int),
-		TLV_SET_U16(0x0005, def_inq_scan_window),
-		TLV_SET_U16(0x0006, def_br_lsto),
-		TLV_SET_U16(0x0007, def_page_timeout),
-		TLV_SET_U16(0x0008, sniff_min_interval),
-		TLV_SET_U16(0x0009, sniff_max_interval),
-		TLV_SET_U16(0x000a, le_adv_min_interval),
-		TLV_SET_U16(0x000b, le_adv_max_interval),
-		TLV_SET_U16(0x000c, def_multi_adv_rotation_duration),
-		TLV_SET_U16(0x000d, le_scan_interval),
-		TLV_SET_U16(0x000e, le_scan_window),
-		TLV_SET_U16(0x000f, le_scan_int_suspend),
-		TLV_SET_U16(0x0010, le_scan_window_suspend),
-		TLV_SET_U16(0x0011, le_scan_int_discovery),
-		TLV_SET_U16(0x0012, le_scan_window_discovery),
-		TLV_SET_U16(0x0013, le_scan_int_adv_monitor),
-		TLV_SET_U16(0x0014, le_scan_window_adv_monitor),
-		TLV_SET_U16(0x0015, le_scan_int_connect),
-		TLV_SET_U16(0x0016, le_scan_window_connect),
-		TLV_SET_U16(0x0017, le_conn_min_interval),
-		TLV_SET_U16(0x0018, le_conn_max_interval),
-		TLV_SET_U16(0x0019, le_conn_latency),
-		TLV_SET_U16(0x001a, le_supv_timeout),
-		TLV_SET_U16_JIFFIES_TO_MSECS(0x001b,
-					     def_le_autoconnect_timeout),
-		TLV_SET_U16(0x001d, advmon_allowlist_duration),
-		TLV_SET_U16(0x001e, advmon_no_filter_duration),
-		TLV_SET_U8(0x001f, enable_advmon_interleave_scan),
-	};
+	} __packed rp;
+
+	TLV_SET_ALL();
 
 	bt_dev_dbg(hdev, "sock %p", sk);
 
-- 
2.43.0


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2025-08-31 17:13 [PATCH][next] Bluetooth: Avoid a couple dozen -Wflex-array-member-not-at-end warnings Gustavo A. R. Silva
2025-08-31 17:51 ` [next] " bluez.test.bot
2025-08-31 18:02 ` [PATCH][next] " Gustavo A. R. Silva

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