wireless: ti: Replace zero-length array with flexible-array member
Subsystems (3)
PATCH 1/1 wireless: ti: 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")
--- drivers/net/wireless/ti/wl1251/cmd.h | 4 ++-- drivers/net/wireless/ti/wl1251/wl12xx_80211.h | 2 +- drivers/net/wireless/ti/wlcore/acx.h | 2 +- drivers/net/wireless/ti/wlcore/boot.h | 2 +- drivers/net/wireless/ti/wlcore/cmd.h | 2 +- drivers/net/wireless/ti/wlcore/conf.h | 2 +- drivers/net/wireless/ti/wlcore/wl12xx_80211.h | 2 +- 7 files changed, 8 insertions(+), 8 deletions(-)
drivers/net/wireless/ti/wl1251/cmd.h +2 -2
@@ -90,7 +90,7 @@ struct wl1251_cmd_header {u16 id;u16 status;/* payload */ -u8 data[0 ]; +u8 data[]; } __packed;struct wl1251_command {
@@ -281,7 +281,7 @@ struct wl1251_cmd_packet_template {struct wl1251_cmd_header header;__le16 size; -u8 data[0 ]; +u8 data[]; } __packed;#define TIM_ELE_ID 5
drivers/net/wireless/ti/wl1251/wl12xx_80211.h +1 -1
@@ -65,7 +65,7 @@ struct ieee80211_header {u8 sa[ETH_ALEN ];u8 bssid[ETH_ALEN ];__le16 seq_ctl; -u8 payload[0 ]; +u8 payload[]; } __packed;struct wl12xx_ie_header {
drivers/net/wireless/ti/wlcore/acx.h +1 -1
@@ -938,7 +938,7 @@ struct acx_rx_filter_cfg {u8 action;u8 num_fields; -u8 fields[0 ]; +u8 fields[]; } __packed;struct acx_roaming_stats {
drivers/net/wireless/ti/wlcore/boot.h +1 -1
@@ -26,7 +26,7 @@ struct wl1271_static_data {u8 fw_version[WL1271_FW_VERSION_MAX_LEN ];u32 hw_version;u8 tx_power_table[WL1271_NO_SUBBANDS ][WL1271_NO_POWER_LEVELS ]; -u8 priv[0 ]; +u8 priv[]; };/* number of times we try to read the INIT interrupt */
drivers/net/wireless/ti/wlcore/cmd.h +1 -1
@@ -209,7 +209,7 @@ struct wl1271_cmd_header {__le16 id;__le16 status;/* payload */ -u8 data[0 ]; +u8 data[]; } __packed;#define WL1271_CMD_MAX_PARAMS 572
drivers/net/wireless/ti/wlcore/conf.h +1 -1
@@ -1150,7 +1150,7 @@ struct wlcore_conf {struct wlcore_conf_file {struct wlcore_conf_header header;struct wlcore_conf core; -u8 priv[0 ]; +u8 priv[]; } __packed;#endif
drivers/net/wireless/ti/wlcore/wl12xx_80211.h +1 -1
@@ -66,7 +66,7 @@ struct ieee80211_header {u8 sa[ETH_ALEN ];u8 bssid[ETH_ALEN ];__le16 seq_ctl; -u8 payload[0 ]; +u8 payload[]; } __packed;struct wl12xx_ie_header {
Signature · 1 line
2.25.0
Quoted 22 lines · Gustavo A. R. Silva
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]
Quoted 7 lines
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] commit76497732932f("cxgb3/l2t: Fix undefined behaviour")Signed-off-by Gustavo A. R. Silva <[email protected]>
Patch applied to wireless-drivers-next.git, thanks.
398978f7dfa5 wireless: ti: Replace zero-length array with flexible-array member
Signature · 3 lines
https://patchwork.kernel.org/patch/11402335/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches