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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 7649773293 ("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
This commit is contained in:
Gustavo A. R. Silva 2020-02-24 19:17:09 -06:00 committed by Kalle Valo
parent 645aa87fdf
commit c5047d5b83
4 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/net/wireless/marvell/libertas/host.h
View File

@ -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 {

2
drivers/net/wireless/marvell/libertas/if_sdio.c
View File

@ -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 {

2
drivers/net/wireless/marvell/libertas/if_spi.c
View File

@ -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 {

2
drivers/net/wireless/marvell/libertas/if_usb.h
View File

@ -91,7 +91,7 @@ struct fwheader {
struct fwdata {
struct fwheader hdr;
__le32 seqnum;
uint8_t data[0];
uint8_t data[];
};
/* fwsyncheader */