Hi,

On 2/20/20 13:04, Adham.Abozaeid@microchip.com wrote:

Hi Gustavo

On 2/20/20 6:29 AM, Gustavo A. R. Silva wrote:

quoted

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 <redacted>

 static void cfg_scan_result(enum scan_event scan_event,

diff --git a/drivers/staging/wilc1000/spi.c b/drivers/staging/wilc1000/spi.c
index 44f7d48851b5..11653ac118cd 100644
--- a/drivers/staging/wilc1000/spi.c
+++ b/drivers/staging/wilc1000/spi.c

@@ -139,7 +139,7 @@ struct wilc_spi_read_rsp_data {
        u8 status;
        u8 resp_header;
        u8 resp_data[4];
-       u8 crc[0];
+       u8 crc[];
 } __packed;

more zero-length arrays in wilc1000, spi.c, struct wilc_spi_cmd, and in fw.h

Oh wow, I hadn't thought about cases like this:

struct wilc_spi_cmd {
        u8 cmd_type;
        union {
                struct {
                        u8 addr[3];
                        u8 crc[0];
                } __packed simple_cmd;
                struct {
                        u8 addr[3];
                        u8 size[2];
                        u8 crc[0];
                } __packed dma_cmd;
                struct {
                        u8 addr[3];
                        u8 size[3];
                        u8 crc[0];
                } __packed dma_cmd_ext;
                struct {
                        u8 addr[2];
                        __be32 data;
                        u8 crc[0];
                } __packed internal_w_cmd;
                struct {
                        u8 addr[3];
                        __be32 data;
                        u8 crc[0];
                } __packed w_cmd;
        } u;
} __packed;

Thanks for the feedback.
--
Gustavo