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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/nfc/fdp/fdp.c b/drivers/nfc/fdp/fdp.c
index 0cc9ac8..7c0b1e6 100644 (file)
--- a/drivers/nfc/fdp/fdp.c
+++ b/drivers/nfc/fdp/fdp.c
@@ -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)

diff --git a/drivers/nfc/st21nfca/dep.c b/drivers/nfc/st21nfca/dep.c
index 60acdfd..a1d69f9 100644 (file)
--- a/drivers/nfc/st21nfca/dep.c
+++ b/drivers/nfc/st21nfca/dep.c
@@ -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 {

diff --git a/include/net/nfc/nci.h b/include/net/nfc/nci.h
index 6ab5a83..0550e03 100644 (file)
--- a/include/net/nfc/nci.h
+++ b/include/net/nfc/nci.h
@@ -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 {

diff --git a/include/net/nfc/nfc.h b/include/net/nfc/nfc.h
index 5d277d6..2cd3a26 100644 (file)
--- a/include/net/nfc/nfc.h
+++ b/include/net/nfc/nfc.h
@@ -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 {