libertas: 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: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200225011709.GA601@embeddedor

diff --git a/drivers/net/wireless/marvell/libertas/host.h b/drivers/net/wireless/marvell/libertas/host.h
index a4fc3f79bb17a6b65a756c37ef00511b0d92699f..dfa22468b14a6de7d0a64058619b8994317de1ab 100644 (file)
--- a/drivers/net/wireless/marvell/libertas/host.h
+++ b/drivers/net/wireless/marvell/libertas/host.h
@@ -461,7 +461,7 @@ struct cmd_ds_802_11_scan {
 
        uint8_t bsstype;
        uint8_t bssid[ETH_ALEN];
-       uint8_t tlvbuffer[0];
+       uint8_t tlvbuffer[];
 } __packed;
 
 struct cmd_ds_802_11_scan_rsp {
@@ -469,7 +469,7 @@ struct cmd_ds_802_11_scan_rsp {
 
        __le16 bssdescriptsize;
        uint8_t nr_sets;
-       uint8_t bssdesc_and_tlvbuffer[0];
+       uint8_t bssdesc_and_tlvbuffer[];
 } __packed;
 
 struct cmd_ds_802_11_get_log {

diff --git a/drivers/net/wireless/marvell/libertas/if_sdio.c b/drivers/net/wireless/marvell/libertas/if_sdio.c
index 30f1025ecb9bcbaec0e73ae4b49360d588010b72..acf61b93b7825ad645f1bd8b6e8daaf1fdcb8fba 100644 (file)
--- a/drivers/net/wireless/marvell/libertas/if_sdio.c
+++ b/drivers/net/wireless/marvell/libertas/if_sdio.c
@@ -103,7 +103,7 @@ MODULE_FIRMWARE("sd8688.bin");
 struct if_sdio_packet {
        struct if_sdio_packet   *next;
        u16                     nb;
-       u8                      buffer[0] __attribute__((aligned(4)));
+       u8                      buffer[] __aligned(4);
 };
 
 struct if_sdio_card {

diff --git a/drivers/net/wireless/marvell/libertas/if_spi.c b/drivers/net/wireless/marvell/libertas/if_spi.c
index 3c3f266bf116a083e88253f1c25864ae548c996b..cd9f8ecf171f3eb91249a73b2afb181f396b5533 100644 (file)
--- a/drivers/net/wireless/marvell/libertas/if_spi.c
+++ b/drivers/net/wireless/marvell/libertas/if_spi.c
@@ -35,7 +35,7 @@
 struct if_spi_packet {
        struct list_head                list;
        u16                             blen;
-       u8                              buffer[0] __attribute__((aligned(4)));
+       u8                              buffer[] __aligned(4);
 };
 
 struct if_spi_card {

diff --git a/drivers/net/wireless/marvell/libertas/if_usb.h b/drivers/net/wireless/marvell/libertas/if_usb.h
index 8dc14bec3e161b2941b882fa11ec4ce16850e9a8..7d0daeb33c3f7735aa6a5f8ff3a95f49c4c331f6 100644 (file)
--- a/drivers/net/wireless/marvell/libertas/if_usb.h
+++ b/drivers/net/wireless/marvell/libertas/if_usb.h
@@ -91,7 +91,7 @@ struct fwheader {
 struct fwdata {
        struct fwheader hdr;
        __le32 seqnum;
-       uint8_t data[0];
+       uint8_t data[];
 };
 
 /* fwsyncheader */