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NFC: Replace zero-length array with flexible-array member

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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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gustavo A. R. Silva
2020-02-26 15:20:00 -06:00
committed by David S. Miller
parent 6dd7f1a1fe
commit da60fbe7ef
4 changed files with 11 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
include/net/nfc/nci.h
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@@ -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 {