Bluetooth: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 15 insertions, 15 deletions

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 6293bdd7d862..d878bf8dce20 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -935,7 +935,7 @@ struct hci_cp_sniff_subrate {
 struct hci_cp_set_event_flt {
 	__u8     flt_type;
 	__u8     cond_type;
-	__u8     condition[0];
+	__u8     condition[];
 } __packed;
 
 /* Filter types */
@@ -1335,7 +1335,7 @@ struct hci_rp_read_local_amp_assoc {
 	__u8     status;
 	__u8     phy_handle;
 	__le16   rem_len;
-	__u8     frag[0];
+	__u8     frag[];
 } __packed;
 
 #define HCI_OP_WRITE_REMOTE_AMP_ASSOC	0x140b
@@ -1343,7 +1343,7 @@ struct hci_cp_write_remote_amp_assoc {
 	__u8     phy_handle;
 	__le16   len_so_far;
 	__le16   rem_len;
-	__u8     frag[0];
+	__u8     frag[];
 } __packed;
 struct hci_rp_write_remote_amp_assoc {
 	__u8     status;
@@ -1613,7 +1613,7 @@ struct hci_cp_le_set_ext_scan_params {
 	__u8    own_addr_type;
 	__u8    filter_policy;
 	__u8    scanning_phys;
-	__u8    data[0];
+	__u8    data[];
 } __packed;
 
 #define LE_SCAN_PHY_1M		0x01
@@ -1641,7 +1641,7 @@ struct hci_cp_le_ext_create_conn {
 	__u8      peer_addr_type;
 	bdaddr_t  peer_addr;
 	__u8      phys;
-	__u8      data[0];
+	__u8      data[];
 } __packed;
 
 struct hci_cp_le_ext_conn_param {
@@ -1693,7 +1693,7 @@ struct hci_rp_le_set_ext_adv_params {
 struct hci_cp_le_set_ext_adv_enable {
 	__u8  enable;
 	__u8  num_of_sets;
-	__u8  data[0];
+	__u8  data[];
 } __packed;
 
 struct hci_cp_ext_adv_set {
@@ -1775,14 +1775,14 @@ struct hci_cp_le_set_cig_params {
 	__le16  m_latency;
 	__le16  s_latency;
 	__u8    num_cis;
-	struct hci_cis_params cis[0];
+	struct hci_cis_params cis[];
 } __packed;
 
 struct hci_rp_le_set_cig_params {
 	__u8    status;
 	__u8    cig_id;
 	__u8    num_handles;
-	__le16  handle[0];
+	__le16  handle[];
 } __packed;
 
 #define HCI_OP_LE_CREATE_CIS			0x2064
@@ -1793,7 +1793,7 @@ struct hci_cis {
 
 struct hci_cp_le_create_cis {
 	__u8    num_cis;
-	struct hci_cis cis[0];
+	struct hci_cis cis[];
 } __packed;
 
 #define HCI_OP_LE_REMOVE_CIG			0x2065
@@ -1937,7 +1937,7 @@ struct hci_comp_pkts_info {
 
 struct hci_ev_num_comp_pkts {
 	__u8     num_hndl;
-	struct hci_comp_pkts_info handles[0];
+	struct hci_comp_pkts_info handles[];
 } __packed;
 
 #define HCI_EV_MODE_CHANGE		0x14
@@ -2170,7 +2170,7 @@ struct hci_comp_blocks_info {
 struct hci_ev_num_comp_blocks {
 	__le16   num_blocks;
 	__u8     num_hndl;
-	struct hci_comp_blocks_info handles[0];
+	struct hci_comp_blocks_info handles[];
 } __packed;
 
 #define HCI_EV_SYNC_TRAIN_COMPLETE	0x4F
@@ -2226,7 +2226,7 @@ struct hci_ev_le_advertising_info {
 	__u8	 bdaddr_type;
 	bdaddr_t bdaddr;
 	__u8	 length;
-	__u8	 data[0];
+	__u8	 data[];
 } __packed;
 
 #define HCI_EV_LE_CONN_UPDATE_COMPLETE	0x03
@@ -2302,7 +2302,7 @@ struct hci_ev_le_ext_adv_report {
 	__u8  	 direct_addr_type;
 	bdaddr_t direct_addr;
 	__u8  	 length;
-	__u8	 data[0];
+	__u8	 data[];
 } __packed;
 
 #define HCI_EV_LE_ENHANCED_CONN_COMPLETE    0x0a
@@ -2362,7 +2362,7 @@ struct hci_evt_le_cis_req {
 #define HCI_EV_STACK_INTERNAL	0xfd
 struct hci_ev_stack_internal {
 	__u16    type;
-	__u8     data[0];
+	__u8     data[];
 } __packed;
 
 #define HCI_EV_SI_DEVICE	0x01
@@ -2409,7 +2409,7 @@ struct hci_sco_hdr {
 struct hci_iso_hdr {
 	__le16	handle;
 	__le16	dlen;
-	__u8	data[0];
+	__u8	data[];
 } __packed;
 
 /* ISO data packet status flags */