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 <[email protected]>
---
.../net/wireless/marvell/libertas_tf/if_usb.h | 2 +-
drivers/net/wireless/marvell/mwifiex/fw.h | 40 +++++++++----------
drivers/net/wireless/marvell/mwl8k.c | 6 +--
3 files changed, 24 insertions(+), 24 deletions(-)
diff --git a/drivers/net/wireless/marvell/libertas_tf/if_usb.h b/drivers/net/wireless/marvell/libertas_tf/if_usb.h
index 585ad36f9055..f6dd7373b09e 100644
--- a/drivers/net/wireless/marvell/libertas_tf/if_usb.h
+++ b/drivers/net/wireless/marvell/libertas_tf/if_usb.h
@@ -81,7 +81,7 @@ struct fwheader {
struct fwdata {
struct fwheader hdr;
__le32 seqnum;
- uint8_t data[0];
+ uint8_t data[];
};
/** fwsyncheader */
diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
index 4dfdf928f705..a415d73a73e6 100644
--- a/drivers/net/wireless/marvell/mwifiex/fw.h
+++ b/drivers/net/wireless/marvell/mwifiex/fw.h
@@ -846,7 +846,7 @@ struct mwifiex_ie_types_random_mac {
struct mwifiex_ietypes_chanstats {
struct mwifiex_ie_types_header header;
- struct mwifiex_fw_chan_stats chanstats[0];
+ struct mwifiex_fw_chan_stats chanstats[];
} __packed;
struct mwifiex_ie_types_wildcard_ssid_params {
@@ -1082,7 +1082,7 @@ struct host_cmd_ds_get_hw_spec {
__le32 reserved_6;
__le32 dot_11ac_dev_cap;
__le32 dot_11ac_mcs_support;
- u8 tlvs[0];
+ u8 tlvs[];
} __packed;
struct host_cmd_ds_802_11_rssi_info {
@@ -1140,7 +1140,7 @@ struct ieee_types_assoc_rsp {
__le16 cap_info_bitmap;
__le16 status_code;
__le16 a_id;
- u8 ie_buffer[0];
+ u8 ie_buffer[];
} __packed;
struct host_cmd_ds_802_11_associate_rsp {
@@ -1455,7 +1455,7 @@ struct host_cmd_ds_chan_rpt_event {
__le32 result;
__le64 start_tsf;
__le32 duration;
- u8 tlvbuf[0];
+ u8 tlvbuf[];
} __packed;
struct host_cmd_sdio_sp_rx_aggr_cfg {
@@ -1625,7 +1625,7 @@ struct host_cmd_ds_802_11_bg_scan_config {
__le32 reserved2;
__le32 report_condition;
__le16 reserved3;
- u8 tlv[0];
+ u8 tlv[];
} __packed;
struct host_cmd_ds_802_11_bg_scan_query {
@@ -1720,7 +1720,7 @@ struct mwifiex_ie_types_sta_info {
struct host_cmd_ds_sta_list {
__le16 sta_count;
- u8 tlv[0];
+ u8 tlv[];
} __packed;
struct mwifiex_ie_types_pwr_capability {
@@ -1743,7 +1743,7 @@ struct mwifiex_ie_types_wmm_param_set {
struct mwifiex_ie_types_mgmt_frame {
struct mwifiex_ie_types_header header;
__le16 frame_control;
- u8 frame_contents[0];
+ u8 frame_contents[];
};
struct mwifiex_ie_types_wmm_queue_status {
@@ -1861,7 +1861,7 @@ struct mwifiex_ie_types_2040bssco {
struct mwifiex_ie_types_extcap {
struct mwifiex_ie_types_header header;
- u8 ext_capab[0];
+ u8 ext_capab[];
} __packed;
struct host_cmd_ds_mem_access {
@@ -1918,12 +1918,12 @@ struct mwifiex_assoc_event {
__le16 frame_control;
__le16 cap_info;
__le16 listen_interval;
- u8 data[0];
+ u8 data[];
} __packed;
struct host_cmd_ds_sys_config {
__le16 action;
- u8 tlv[0];
+ u8 tlv[];
};
struct host_cmd_11ac_vht_cfg {
@@ -1956,7 +1956,7 @@ struct host_cmd_tlv_gwk_cipher {
struct host_cmd_tlv_passphrase {
struct mwifiex_ie_types_header header;
- u8 passphrase[0];
+ u8 passphrase[];
} __packed;
struct host_cmd_tlv_wep_key {
@@ -1978,12 +1978,12 @@ struct host_cmd_tlv_encrypt_protocol {
struct host_cmd_tlv_ssid {
struct mwifiex_ie_types_header header;
- u8 ssid[0];
+ u8 ssid[];
} __packed;
struct host_cmd_tlv_rates {
struct mwifiex_ie_types_header header;
- u8 rates[0];
+ u8 rates[];
} __packed;
struct mwifiex_ie_types_bssid_list {
@@ -2100,13 +2100,13 @@ struct mwifiex_fw_mef_entry {
u8 mode;
u8 action;
__le16 exprsize;
- u8 expr[0];
+ u8 expr[];
} __packed;
struct host_cmd_ds_mef_cfg {
__le32 criteria;
__le16 num_entries;
- struct mwifiex_fw_mef_entry mef_entry[0];
+ struct mwifiex_fw_mef_entry mef_entry[];
} __packed;
#define CONNECTION_TYPE_INFRA 0
@@ -2169,7 +2169,7 @@ struct mwifiex_radar_det_event {
struct mwifiex_ie_types_multi_chan_info {
struct mwifiex_ie_types_header header;
__le16 status;
- u8 tlv_buffer[0];
+ u8 tlv_buffer[];
} __packed;
struct mwifiex_ie_types_mc_group_info {
@@ -2185,7 +2185,7 @@ struct mwifiex_ie_types_mc_group_info {
u8 usb_ep_num;
} hid_num;
u8 intf_num;
- u8 bss_type_numlist[0];
+ u8 bss_type_numlist[];
} __packed;
struct meas_rpt_map {
@@ -2250,13 +2250,13 @@ struct coalesce_receive_filt_rule {
u8 num_of_fields;
u8 pkt_type;
__le16 max_coalescing_delay;
- struct coalesce_filt_field_param params[0];
+ struct coalesce_filt_field_param params[];
} __packed;
struct host_cmd_ds_coalesce_cfg {
__le16 action;
__le16 num_of_rules;
- struct coalesce_receive_filt_rule rule[0];
+ struct coalesce_receive_filt_rule rule[];
} __packed;
struct host_cmd_ds_multi_chan_policy {
@@ -2295,7 +2295,7 @@ struct host_cmd_ds_pkt_aggr_ctrl {
struct host_cmd_ds_sta_configure {
__le16 action;
- u8 tlv_buffer[0];
+ u8 tlv_buffer[];
} __packed;
struct host_cmd_ds_command {
diff --git a/drivers/net/wireless/marvell/mwl8k.c b/drivers/net/wireless/marvell/mwl8k.c
index d55f229abeea..47fb4b3ea004 100644
--- a/drivers/net/wireless/marvell/mwl8k.c
+++ b/drivers/net/wireless/marvell/mwl8k.c
@@ -592,7 +592,7 @@ struct mwl8k_cmd_pkt {
__u8 seq_num;
__u8 macid;
__le16 result;
- char payload[0];
+ char payload[];
} __packed;
/*
@@ -806,7 +806,7 @@ static int mwl8k_load_firmware(struct ieee80211_hw *hw)
struct mwl8k_dma_data {
__le16 fwlen;
struct ieee80211_hdr wh;
- char data[0];
+ char data[];
} __packed;
/* Routines to add/remove DMA header from skb. */
@@ -2955,7 +2955,7 @@ mwl8k_cmd_rf_antenna(struct ieee80211_hw *hw, int antenna, int mask)
struct mwl8k_cmd_set_beacon {
struct mwl8k_cmd_pkt header;
__le16 beacon_len;
- __u8 beacon[0];
+ __u8 beacon[];
};
static int mwl8k_cmd_set_beacon(struct ieee80211_hw *hw,
--
2.25.0
Hi Gustavo,
> 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]
Thanks for this path.
Acked-by: Ganapathi Bhat <[email protected]>