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Message-ID: <20200226212000.GA32231@embeddedor>
Date: Wed, 26 Feb 2020 15:20:00 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
"Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH][next] 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@...eddedor.com>
---
drivers/nfc/fdp/fdp.c | 2 +-
drivers/nfc/st21nfca/dep.c | 4 ++--
include/net/nfc/nci.h | 14 +++++++-------
include/net/nfc/nfc.h | 2 +-
4 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/drivers/nfc/fdp/fdp.c b/drivers/nfc/fdp/fdp.c
index 062535c8251b..d4ff9e6056c2 100644
--- 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 137eb3f7dabd..98e73e047e02 100644
--- 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 6ab5a83f597c..0550e0380b8d 100644
--- 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 5d277d68fd8d..2cd3a261bcbc 100644
--- 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 {
--
2.25.0
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