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 --- drivers/staging/gdm724x/gdm_mux.h | 2 +- drivers/staging/gdm724x/hci_packet.h | 6 ++-- drivers/staging/greybus/audio_apbridgea.h | 2 +- drivers/staging/ks7010/ks_hostif.h | 4 +-- .../staging/media/allegro-dvt/allegro-core.c | 2 +- drivers/staging/octeon-usb/octeon-hcd.c | 2 +- drivers/staging/rtl8192e/rtllib.h | 30 +++++++++---------- .../staging/rtl8192u/ieee80211/ieee80211.h | 28 ++++++++--------- drivers/staging/rtl8712/ieee80211.h | 4 +-- drivers/staging/rtl8712/rtl871x_mp_ioctl.h | 4 +-- drivers/staging/wilc1000/cfg80211.c | 10 +++---- drivers/staging/wilc1000/spi.c | 2 +- drivers/staging/wlan-ng/hfa384x.h | 4 +-- drivers/staging/wlan-ng/p80211types.h | 4 +-- 14 files changed, 52 insertions(+), 52 deletions(-)
diff --git a/drivers/staging/gdm724x/gdm_mux.h b/drivers/staging/gdm724x/gdm_mux.h index 51c22e3d8aeb..87b8d921fdc8 100644 --- a/drivers/staging/gdm724x/gdm_mux.h +++ b/drivers/staging/gdm724x/gdm_mux.h @@ -29,7 +29,7 @@ struct mux_pkt_header { __le32 seq_num; __le32 payload_size; __le16 packet_type; - unsigned char data[0]; + unsigned char data[]; };
struct mux_tx { diff --git a/drivers/staging/gdm724x/hci_packet.h b/drivers/staging/gdm724x/hci_packet.h index 6dea3694afdd..faecdfbc664f 100644 --- a/drivers/staging/gdm724x/hci_packet.h +++ b/drivers/staging/gdm724x/hci_packet.h @@ -28,7 +28,7 @@ struct hci_packet { __dev16 cmd_evt; __dev16 len; - u8 data[0]; + u8 data[]; } __packed;
struct tlv { @@ -51,7 +51,7 @@ struct sdu { __dev32 dft_eps_ID; __dev32 bearer_ID; __dev32 nic_type; - u8 data[0]; + u8 data[]; } __packed;
struct multi_sdu { @@ -59,7 +59,7 @@ struct multi_sdu { __dev16 len; __dev16 num_packet; __dev16 reserved; - u8 data[0]; + u8 data[]; } __packed;
struct hci_pdn_table_ind { diff --git a/drivers/staging/greybus/audio_apbridgea.h b/drivers/staging/greybus/audio_apbridgea.h index 3f1f4dd2c61a..efec0f815efd 100644 --- a/drivers/staging/greybus/audio_apbridgea.h +++ b/drivers/staging/greybus/audio_apbridgea.h @@ -65,7 +65,7 @@ struct audio_apbridgea_hdr { __u8 type; __le16 i2s_port; - __u8 data[0]; + __u8 data[]; } __packed;
struct audio_apbridgea_set_config_request { diff --git a/drivers/staging/ks7010/ks_hostif.h b/drivers/staging/ks7010/ks_hostif.h index ca7dc8f5166c..39138191a556 100644 --- a/drivers/staging/ks7010/ks_hostif.h +++ b/drivers/staging/ks7010/ks_hostif.h @@ -70,7 +70,7 @@ struct hostif_data_request { #define TYPE_DATA 0x0000 #define TYPE_AUTH 0x0001 __le16 reserved; - u8 data[0]; + u8 data[]; } __packed;
#define TYPE_PMK1 0x0001 @@ -194,7 +194,7 @@ enum mib_data_type { struct hostif_mib_value { __le16 size; __le16 type; - u8 body[0]; + u8 body[]; } __packed;
struct hostif_mib_get_confirm_t { diff --git a/drivers/staging/media/allegro-dvt/allegro-core.c b/drivers/staging/media/allegro-dvt/allegro-core.c index 3be41698df4c..0a09b3622e78 100644 --- a/drivers/staging/media/allegro-dvt/allegro-core.c +++ b/drivers/staging/media/allegro-dvt/allegro-core.c @@ -434,7 +434,7 @@ struct mcu_msg_push_buffers_internal_buffer { struct mcu_msg_push_buffers_internal { struct mcu_msg_header header; u32 channel_id; - struct mcu_msg_push_buffers_internal_buffer buffer[0]; + struct mcu_msg_push_buffers_internal_buffer buffer[]; } __attribute__ ((__packed__));
struct mcu_msg_put_stream_buffer { diff --git a/drivers/staging/octeon-usb/octeon-hcd.c b/drivers/staging/octeon-usb/octeon-hcd.c index 582c9187559d..61471a19d4e6 100644 --- a/drivers/staging/octeon-usb/octeon-hcd.c +++ b/drivers/staging/octeon-usb/octeon-hcd.c @@ -406,7 +406,7 @@ struct octeon_hcd { */ struct octeon_temp_buffer { void *orig_buffer; - u8 data[0]; + u8 data[]; };
static inline struct usb_hcd *octeon_to_hcd(struct octeon_hcd *p) diff --git a/drivers/staging/rtl8192e/rtllib.h b/drivers/staging/rtl8192e/rtllib.h index 328f410daa03..b84f00b8d18b 100644 --- a/drivers/staging/rtl8192e/rtllib.h +++ b/drivers/staging/rtl8192e/rtllib.h @@ -728,14 +728,14 @@ struct rtllib_pspoll_hdr { struct rtllib_hdr { __le16 frame_ctl; __le16 duration_id; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_hdr_1addr { __le16 frame_ctl; __le16 duration_id; u8 addr1[ETH_ALEN]; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_hdr_2addr { @@ -743,7 +743,7 @@ struct rtllib_hdr_2addr { __le16 duration_id; u8 addr1[ETH_ALEN]; u8 addr2[ETH_ALEN]; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_hdr_3addr { @@ -753,7 +753,7 @@ struct rtllib_hdr_3addr { u8 addr2[ETH_ALEN]; u8 addr3[ETH_ALEN]; __le16 seq_ctl; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_hdr_4addr { @@ -764,7 +764,7 @@ struct rtllib_hdr_4addr { u8 addr3[ETH_ALEN]; __le16 seq_ctl; u8 addr4[ETH_ALEN]; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_hdr_3addrqos { @@ -775,7 +775,7 @@ struct rtllib_hdr_3addrqos { u8 addr3[ETH_ALEN]; __le16 seq_ctl; __le16 qos_ctl; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_hdr_4addrqos { @@ -787,13 +787,13 @@ struct rtllib_hdr_4addrqos { __le16 seq_ctl; u8 addr4[ETH_ALEN]; __le16 qos_ctl; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtllib_info_element { u8 id; u8 len; - u8 data[0]; + u8 data[]; } __packed;
struct rtllib_authentication { @@ -802,7 +802,7 @@ struct rtllib_authentication { __le16 transaction; __le16 status; /*challenge*/ - struct rtllib_info_element info_element[0]; + struct rtllib_info_element info_element[]; } __packed;
struct rtllib_disauth { @@ -818,7 +818,7 @@ struct rtllib_disassoc { struct rtllib_probe_request { struct rtllib_hdr_3addr header; /* SSID, supported rates */ - struct rtllib_info_element info_element[0]; + struct rtllib_info_element info_element[]; } __packed;
struct rtllib_probe_response { @@ -829,7 +829,7 @@ struct rtllib_probe_response { /* SSID, supported rates, FH params, DS params, * CF params, IBSS params, TIM (if beacon), RSN */ - struct rtllib_info_element info_element[0]; + struct rtllib_info_element info_element[]; } __packed;
/* Alias beacon for probe_response */ @@ -840,7 +840,7 @@ struct rtllib_assoc_request_frame { __le16 capability; __le16 listen_interval; /* SSID, supported rates, RSN */ - struct rtllib_info_element info_element[0]; + struct rtllib_info_element info_element[]; } __packed;
struct rtllib_assoc_response_frame { @@ -848,7 +848,7 @@ struct rtllib_assoc_response_frame { __le16 capability; __le16 status; __le16 aid; - struct rtllib_info_element info_element[0]; /* supported rates */ + struct rtllib_info_element info_element[]; /* supported rates */ } __packed;
struct rtllib_txb { @@ -859,7 +859,7 @@ struct rtllib_txb { u16 reserved; __le16 frag_size; __le16 payload_size; - struct sk_buff *fragments[0]; + struct sk_buff *fragments[]; };
#define MAX_SUBFRAME_COUNT 64 @@ -1792,7 +1792,7 @@ struct rtllib_device { /* This must be the last item so that it points to the data * allocated beyond this structure by alloc_rtllib */ - u8 priv[0]; + u8 priv[]; };
#define IEEE_A (1<<0) diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211.h b/drivers/staging/rtl8192u/ieee80211/ieee80211.h index 9576b647f6b1..39f4ddd86796 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211.h +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211.h @@ -886,14 +886,14 @@ enum ieee80211_mfie { struct rtl_80211_hdr { __le16 frame_ctl; __le16 duration_id; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtl_80211_hdr_1addr { __le16 frame_ctl; __le16 duration_id; u8 addr1[ETH_ALEN]; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtl_80211_hdr_2addr { @@ -901,7 +901,7 @@ struct rtl_80211_hdr_2addr { __le16 duration_id; u8 addr1[ETH_ALEN]; u8 addr2[ETH_ALEN]; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtl_80211_hdr_3addr { @@ -911,7 +911,7 @@ struct rtl_80211_hdr_3addr { u8 addr2[ETH_ALEN]; u8 addr3[ETH_ALEN]; __le16 seq_ctl; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtl_80211_hdr_4addr { @@ -922,7 +922,7 @@ struct rtl_80211_hdr_4addr { u8 addr3[ETH_ALEN]; __le16 seq_ctl; u8 addr4[ETH_ALEN]; - u8 payload[0]; + u8 payload[]; } __packed;
struct rtl_80211_hdr_3addrqos { @@ -951,7 +951,7 @@ struct rtl_80211_hdr_4addrqos { struct ieee80211_info_element { u8 id; u8 len; - u8 data[0]; + u8 data[]; } __packed;
struct ieee80211_authentication { @@ -960,7 +960,7 @@ struct ieee80211_authentication { __le16 transaction; __le16 status; /*challenge*/ - struct ieee80211_info_element info_element[0]; + struct ieee80211_info_element info_element[]; } __packed;
struct ieee80211_disassoc { @@ -971,7 +971,7 @@ struct ieee80211_disassoc { struct ieee80211_probe_request { struct rtl_80211_hdr_3addr header; /* SSID, supported rates */ - struct ieee80211_info_element info_element[0]; + struct ieee80211_info_element info_element[]; } __packed;
struct ieee80211_probe_response { @@ -982,7 +982,7 @@ struct ieee80211_probe_response { /* SSID, supported rates, FH params, DS params, * CF params, IBSS params, TIM (if beacon), RSN */ - struct ieee80211_info_element info_element[0]; + struct ieee80211_info_element info_element[]; } __packed;
/* Alias beacon for probe_response */ @@ -993,7 +993,7 @@ struct ieee80211_assoc_request_frame { __le16 capability; __le16 listen_interval; /* SSID, supported rates, RSN */ - struct ieee80211_info_element info_element[0]; + struct ieee80211_info_element info_element[]; } __packed;
struct ieee80211_reassoc_request_frame { @@ -1002,7 +1002,7 @@ struct ieee80211_reassoc_request_frame { __le16 listen_interval; u8 current_ap[ETH_ALEN]; /* SSID, supported rates, RSN */ - struct ieee80211_info_element info_element[0]; + struct ieee80211_info_element info_element[]; } __packed;
struct ieee80211_assoc_response_frame { @@ -1010,7 +1010,7 @@ struct ieee80211_assoc_response_frame { __le16 capability; __le16 status; __le16 aid; - struct ieee80211_info_element info_element[0]; /* supported rates */ + struct ieee80211_info_element info_element[]; /* supported rates */ } __packed;
struct ieee80211_txb { @@ -1021,7 +1021,7 @@ struct ieee80211_txb { u16 reserved; __le16 frag_size; __le16 payload_size; - struct sk_buff *fragments[0]; + struct sk_buff *fragments[]; };
#define MAX_TX_AGG_COUNT 16 @@ -2007,7 +2007,7 @@ struct ieee80211_device { /* This must be the last item so that it points to the data * allocated beyond this structure by alloc_ieee80211 */ - u8 priv[0]; + u8 priv[]; };
#define IEEE_A (1<<0) diff --git a/drivers/staging/rtl8712/ieee80211.h b/drivers/staging/rtl8712/ieee80211.h index 8098f6905554..dabaa8fd34fb 100644 --- a/drivers/staging/rtl8712/ieee80211.h +++ b/drivers/staging/rtl8712/ieee80211.h @@ -535,7 +535,7 @@ struct ieee80211_info_element_hdr { struct ieee80211_info_element { u8 id; u8 len; - u8 data[0]; + u8 data[]; } __packed;
/* @@ -597,7 +597,7 @@ struct ieee80211_txb { u16 reserved; u16 frag_size; u16 payload_size; - struct sk_buff *fragments[0]; + struct sk_buff *fragments[]; };
/* SWEEP TABLE ENTRIES NUMBER*/ diff --git a/drivers/staging/rtl8712/rtl871x_mp_ioctl.h b/drivers/staging/rtl8712/rtl871x_mp_ioctl.h index 64e2ae436625..59fa6664d868 100644 --- a/drivers/staging/rtl8712/rtl871x_mp_ioctl.h +++ b/drivers/staging/rtl8712/rtl871x_mp_ioctl.h @@ -48,7 +48,7 @@ struct eeprom_rw_param { struct EFUSE_ACCESS_STRUCT { u16 start_addr; u16 cnts; - u8 data[0]; + u8 data[]; };
struct burst_rw_reg { @@ -324,7 +324,7 @@ struct mp_ioctl_handler { struct mp_ioctl_param { unsigned int subcode; unsigned int len; - unsigned char data[0]; + unsigned char data[]; };
#define GEN_MP_IOCTL_SUBCODE(code) _MP_IOCTL_ ## code ## _CMD_ diff --git a/drivers/staging/wilc1000/cfg80211.c b/drivers/staging/wilc1000/cfg80211.c index 995b1f306807..5d8faa01337d 100644 --- a/drivers/staging/wilc1000/cfg80211.c +++ b/drivers/staging/wilc1000/cfg80211.c @@ -62,7 +62,7 @@ struct wilc_p2p_pub_act_frame { u8 oui_type; u8 oui_subtype; u8 dialog_token; - u8 elem[0]; + u8 elem[]; } __packed;
struct wilc_vendor_specific_ie { @@ -70,13 +70,13 @@ struct wilc_vendor_specific_ie { u8 tag_len; u8 oui[3]; u8 oui_type; - u8 attr[0]; + u8 attr[]; } __packed;
struct wilc_attr_entry { u8 attr_type; __le16 attr_len; - u8 val[0]; + u8 val[]; } __packed;
struct wilc_attr_oper_ch { @@ -91,13 +91,13 @@ struct wilc_attr_ch_list { u8 attr_type; __le16 attr_len; u8 country_code[IEEE80211_COUNTRY_STRING_LEN]; - u8 elem[0]; + u8 elem[]; } __packed;
struct wilc_ch_list_elem { u8 op_class; u8 no_of_channels; - u8 ch_list[0]; + u8 ch_list[]; } __packed;
static void cfg_scan_result(enum scan_event scan_event, diff --git a/drivers/staging/wilc1000/spi.c b/drivers/staging/wilc1000/spi.c index 44f7d48851b5..11653ac118cd 100644 --- a/drivers/staging/wilc1000/spi.c +++ b/drivers/staging/wilc1000/spi.c @@ -139,7 +139,7 @@ struct wilc_spi_read_rsp_data { u8 status; u8 resp_header; u8 resp_data[4]; - u8 crc[0]; + u8 crc[]; } __packed;
struct wilc_spi_rsp_data { diff --git a/drivers/staging/wlan-ng/hfa384x.h b/drivers/staging/wlan-ng/hfa384x.h index bdd7f414fdbb..88e894dd3568 100644 --- a/drivers/staging/wlan-ng/hfa384x.h +++ b/drivers/staging/wlan-ng/hfa384x.h @@ -355,7 +355,7 @@ /* Commonly used basic types */ struct hfa384x_bytestr { __le16 len; - u8 data[0]; + u8 data[]; } __packed;
struct hfa384x_bytestr32 { @@ -421,7 +421,7 @@ struct hfa384x_authenticate_station_data { /*-- Configuration Record: WPAData (data portion only) --*/ struct hfa384x_wpa_data { __le16 datalen; - u8 data[0]; /* max 80 */ + u8 data[]; /* max 80 */ } __packed;
/*-------------------------------------------------------------------- diff --git a/drivers/staging/wlan-ng/p80211types.h b/drivers/staging/wlan-ng/p80211types.h index ac254542fde6..3dcdd022da61 100644 --- a/drivers/staging/wlan-ng/p80211types.h +++ b/drivers/staging/wlan-ng/p80211types.h @@ -204,7 +204,7 @@ struct p80211pstr {
struct p80211pstrd { u8 len; - u8 data[0]; + u8 data[]; } __packed;
/* Maximum pascal string */ @@ -249,7 +249,7 @@ struct p80211itemd { u32 did; u16 status; u16 len; - u8 data[0]; + u8 data[]; } __packed;
/* message data item for int, BOUNDEDINT, ENUMINT */
Hi Gustavo
On 2/20/20 6:29 AM, Gustavo A. R. Silva wrote:
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
static void cfg_scan_result(enum scan_event scan_event, diff --git a/drivers/staging/wilc1000/spi.c b/drivers/staging/wilc1000/spi.c index 44f7d48851b5..11653ac118cd 100644 --- a/drivers/staging/wilc1000/spi.c +++ b/drivers/staging/wilc1000/spi.c @@ -139,7 +139,7 @@ struct wilc_spi_read_rsp_data { u8 status; u8 resp_header; u8 resp_data[4];
u8 crc[0];
u8 crc[];} __packed;
more zero-length arrays in wilc1000, spi.c, struct wilc_spi_cmd, and in fw.h
Hi,
On 2/20/20 13:04, Adham.Abozaeid@microchip.com wrote:
Hi Gustavo
On 2/20/20 6:29 AM, Gustavo A. R. Silva wrote:
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
static void cfg_scan_result(enum scan_event scan_event, diff --git a/drivers/staging/wilc1000/spi.c b/drivers/staging/wilc1000/spi.c index 44f7d48851b5..11653ac118cd 100644 --- a/drivers/staging/wilc1000/spi.c +++ b/drivers/staging/wilc1000/spi.c @@ -139,7 +139,7 @@ struct wilc_spi_read_rsp_data { u8 status; u8 resp_header; u8 resp_data[4];
u8 crc[0];
u8 crc[];} __packed;
more zero-length arrays in wilc1000, spi.c, struct wilc_spi_cmd, and in fw.h
Oh wow, I hadn't thought about cases like this:
struct wilc_spi_cmd { u8 cmd_type; union { struct { u8 addr[3]; u8 crc[0]; } __packed simple_cmd; struct { u8 addr[3]; u8 size[2]; u8 crc[0]; } __packed dma_cmd; struct { u8 addr[3]; u8 size[3]; u8 crc[0]; } __packed dma_cmd_ext; struct { u8 addr[2]; __be32 data; u8 crc[0]; } __packed internal_w_cmd; struct { u8 addr[3]; __be32 data; u8 crc[0]; } __packed w_cmd; } u; } __packed;
Thanks for the feedback. -- Gustavo
-
Adham.Abozaeid＠microchip.com -
Gustavo A. R. Silva