Commit da60fbe7 authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by David S. Miller
Browse files

NFC: 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 76497732 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6dd7f1a1

drivers/nfc/fdp/fdp.c

+1 −1
Original line number Diff line number Diff line
@@ -76,7 +76,7 @@ static u8 nci_core_get_config_otp_ram_version[5] = { 
struct nci_core_get_config_rsp {

	u8 status;

	u8 count;

	u8 data[0];

	u8 data[];

};



static int fdp_nci_create_conn(struct nci_dev *ndev)

drivers/nfc/st21nfca/dep.c

+2 −2
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ struct st21nfca_atr_req { 
	u8 bsi;

	u8 bri;

	u8 ppi;

	u8 gbi[0];

	u8 gbi[];

} __packed;



struct st21nfca_atr_res {
@@ -79,7 +79,7 @@ struct st21nfca_atr_res { 
	u8 bri;

	u8 to;

	u8 ppi;

	u8 gbi[0];

	u8 gbi[];

} __packed;



struct st21nfca_psl_req {

include/net/nfc/nci.h

+7 −7
Original line number Diff line number Diff line
@@ -244,13 +244,13 @@ struct dest_spec_params { 
struct core_conn_create_dest_spec_params {

	__u8    type;

	__u8    length;

	__u8    value[0];

	__u8    value[];

} __packed;



struct nci_core_conn_create_cmd {

	__u8    destination_type;

	__u8    number_destination_params;

	struct core_conn_create_dest_spec_params params[0];

	struct core_conn_create_dest_spec_params params[];

} __packed;



#define NCI_OP_CORE_CONN_CLOSE_CMD	nci_opcode_pack(NCI_GID_CORE, 0x05)
@@ -321,7 +321,7 @@ struct nci_core_init_rsp_1 { 
	__u8	status;

	__le32	nfcc_features;

	__u8	num_supported_rf_interfaces;

	__u8	supported_rf_interfaces[0];	/* variable size array */

	__u8	supported_rf_interfaces[];	/* variable size array */

	/* continuted in nci_core_init_rsp_2 */

} __packed;
@@ -338,7 +338,7 @@ struct nci_core_init_rsp_2 { 
struct nci_core_set_config_rsp {

	__u8	status;

	__u8	num_params;

	__u8	params_id[0];	/* variable size array */

	__u8	params_id[];	/* variable size array */

} __packed;



#define NCI_OP_CORE_CONN_CREATE_RSP	nci_opcode_pack(NCI_GID_CORE, 0x04)
@@ -501,18 +501,18 @@ struct nci_rf_nfcee_action_ntf { 
	__u8 nfcee_id;

	__u8 trigger;

	__u8 supported_data_length;

	__u8 supported_data[0];

	__u8 supported_data[];

} __packed;



#define NCI_OP_NFCEE_DISCOVER_NTF nci_opcode_pack(NCI_GID_NFCEE_MGMT, 0x00)

struct nci_nfcee_supported_protocol {

	__u8	num_protocol;

	__u8	supported_protocol[0];

	__u8	supported_protocol[];

} __packed;



struct nci_nfcee_information_tlv {

	__u8	num_tlv;

	__u8	information_tlv[0];

	__u8	information_tlv[];

} __packed;



struct nci_nfcee_discover_ntf {

include/net/nfc/nfc.h

+1 −1
Original line number Diff line number Diff line
@@ -146,7 +146,7 @@ struct nfc_evt_transaction { 
	u32 aid_len;

	u8 aid[NFC_MAX_AID_LENGTH];

	u8 params_len;

	u8 params[0];

	u8 params[];

} __packed;



struct nfc_genl_data {

CRA Git | Maintained and supported by SUSTech CRA and CCSE