ath10k: Replace zero-length array with flexible-array

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]

sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.

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: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200507041127.GA31587@embeddedor

1 files changed, 21 insertions, 21 deletions

diff --git a/drivers/net/wireless/ath/ath10k/wmi.h b/drivers/net/wireless/ath/ath10k/wmi.h
index 0f05405bebc0..511144b36231 100644
--- a/drivers/net/wireless/ath/ath10k/wmi.h
+++ b/drivers/net/wireless/ath/ath10k/wmi.h
@@ -2292,7 +2292,7 @@ struct wmi_service_ready_event {
 	 * where FW can access this memory directly (or) by DMA.
 	 */
 	__le32 num_mem_reqs;
-	struct wlan_host_mem_req mem_reqs[0];
+	struct wlan_host_mem_req mem_reqs[];
 } __packed;
 
 /* This is the definition from 10.X firmware branch */
@@ -2331,7 +2331,7 @@ struct wmi_10x_service_ready_event {
 	 */
 	__le32 num_mem_reqs;
 
-	struct wlan_host_mem_req mem_reqs[0];
+	struct wlan_host_mem_req mem_reqs[];
 } __packed;
 
 #define WMI_SERVICE_READY_TIMEOUT_HZ (5 * HZ)
@@ -3086,19 +3086,19 @@ struct wmi_chan_list_entry {
 struct wmi_chan_list {
 	__le32 tag; /* WMI_CHAN_LIST_TAG */
 	__le32 num_chan;
-	struct wmi_chan_list_entry channel_list[0];
+	struct wmi_chan_list_entry channel_list[];
 } __packed;
 
 struct wmi_bssid_list {
 	__le32 tag; /* WMI_BSSID_LIST_TAG */
 	__le32 num_bssid;
-	struct wmi_mac_addr bssid_list[0];
+	struct wmi_mac_addr bssid_list[];
 } __packed;
 
 struct wmi_ie_data {
 	__le32 tag; /* WMI_IE_TAG */
 	__le32 ie_len;
-	u8 ie_data[0];
+	u8 ie_data[];
 } __packed;
 
 struct wmi_ssid {
@@ -3109,7 +3109,7 @@ struct wmi_ssid {
 struct wmi_ssid_list {
 	__le32 tag; /* WMI_SSID_LIST_TAG */
 	__le32 num_ssids;
-	struct wmi_ssid ssids[0];
+	struct wmi_ssid ssids[];
 } __packed;
 
 /* prefix used by scan requestor ids on the host */
@@ -3311,7 +3311,7 @@ struct wmi_stop_scan_arg {
 
 struct wmi_scan_chan_list_cmd {
 	__le32 num_scan_chans;
-	struct wmi_channel chan_info[0];
+	struct wmi_channel chan_info[];
 } __packed;
 
 struct wmi_scan_chan_list_arg {
@@ -3395,12 +3395,12 @@ struct wmi_mgmt_rx_hdr_v2 {
 
 struct wmi_mgmt_rx_event_v1 {
 	struct wmi_mgmt_rx_hdr_v1 hdr;
-	u8 buf[0];
+	u8 buf[];
 } __packed;
 
 struct wmi_mgmt_rx_event_v2 {
 	struct wmi_mgmt_rx_hdr_v2 hdr;
-	u8 buf[0];
+	u8 buf[];
 } __packed;
 
 struct wmi_10_4_mgmt_rx_hdr {
@@ -3415,7 +3415,7 @@ struct wmi_10_4_mgmt_rx_hdr {
 
 struct wmi_10_4_mgmt_rx_event {
 	struct wmi_10_4_mgmt_rx_hdr hdr;
-	u8 buf[0];
+	u8 buf[];
 } __packed;
 
 struct wmi_mgmt_rx_ext_info {
@@ -3455,14 +3455,14 @@ struct wmi_phyerr {
 	__le32 rssi_chains[4];
 	__le16 nf_chains[4];
 	__le32 buf_len;
-	u8 buf[0];
+	u8 buf[];
 } __packed;
 
 struct wmi_phyerr_event {
 	__le32 num_phyerrs;
 	__le32 tsf_l32;
 	__le32 tsf_u32;
-	struct wmi_phyerr phyerrs[0];
+	struct wmi_phyerr phyerrs[];
 } __packed;
 
 struct wmi_10_4_phyerr_event {
@@ -3479,7 +3479,7 @@ struct wmi_10_4_phyerr_event {
 	__le32 phy_err_mask[2];
 	__le32 tsf_timestamp;
 	__le32 buf_len;
-	u8 buf[0];
+	u8 buf[];
 } __packed;
 
 struct wmi_radar_found_info {
@@ -3592,7 +3592,7 @@ struct wmi_mgmt_tx_hdr {
 
 struct wmi_mgmt_tx_cmd {
 	struct wmi_mgmt_tx_hdr hdr;
-	u8 buf[0];
+	u8 buf[];
 } __packed;
 
 struct wmi_echo_event {
@@ -4628,7 +4628,7 @@ struct wmi_stats_event {
 	 *  By having a zero sized array, the pointer to data area
 	 *  becomes available without increasing the struct size
 	 */
-	u8 data[0];
+	u8 data[];
 } __packed;
 
 struct wmi_10_2_stats_event {
@@ -4638,7 +4638,7 @@ struct wmi_10_2_stats_event {
 	__le32 num_vdev_stats;
 	__le32 num_peer_stats;
 	__le32 num_bcnflt_stats;
-	u8 data[0];
+	u8 data[];
 } __packed;
 
 /*
@@ -5033,7 +5033,7 @@ struct wmi_vdev_install_key_cmd {
 	__le32 key_rxmic_len;
 
 	/* contains key followed by tx mic followed by rx mic */
-	u8 key_data[0];
+	u8 key_data[];
 } __packed;
 
 struct wmi_vdev_install_key_arg {
@@ -5703,7 +5703,7 @@ struct wmi_bcn_tx_hdr {
 
 struct wmi_bcn_tx_cmd {
 	struct wmi_bcn_tx_hdr hdr;
-	u8 *bcn[0];
+	u8 *bcn[];
 } __packed;
 
 struct wmi_bcn_tx_arg {
@@ -6120,7 +6120,7 @@ struct wmi_bcn_info {
 
 struct wmi_host_swba_event {
 	__le32 vdev_map;
-	struct wmi_bcn_info bcn_info[0];
+	struct wmi_bcn_info bcn_info[];
 } __packed;
 
 struct wmi_10_2_4_bcn_info {
@@ -6130,7 +6130,7 @@ struct wmi_10_2_4_bcn_info {
 
 struct wmi_10_2_4_host_swba_event {
 	__le32 vdev_map;
-	struct wmi_10_2_4_bcn_info bcn_info[0];
+	struct wmi_10_2_4_bcn_info bcn_info[];
 } __packed;
 
 /* 16 words = 512 client + 1 word = for guard */
@@ -6171,7 +6171,7 @@ struct wmi_10_4_bcn_info {
 
 struct wmi_10_4_host_swba_event {
 	__le32 vdev_map;
-	struct wmi_10_4_bcn_info bcn_info[0];
+	struct wmi_10_4_bcn_info bcn_info[];
 } __packed;
 
 #define WMI_MAX_AP_VDEV 16