[PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member

[PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member

[Gustavo A. R. Silva]

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
inadvertenly introduced[3] to the codebase from now on.

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>
---
 drivers/firmware/arm_scmi/driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 8f952f2f1a29..b40f71edc92d 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -148,7 +148,7 @@ struct scmi_shared_mem {
 #define SCMI_SHMEM_FLAG_INTR_ENABLED	BIT(0)
 	__le32 length;
 	__le32 msg_header;
-	u8 msg_payload[0];
+	u8 msg_payload[];
 };
 
 static const int scmi_linux_errmap[] = {
-- 
2.25.0

Re: [PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member

[Sudeep Holla]

On Tue, Feb 11, 2020 at 05:10:45PM -0600, Gustavo A. R. Silva wrote:
> 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
> inadvertenly introduced[3] to the codebase from now on.
> 
> 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>

Applied these 3 patches [0][1][2] for v5.7

--
Regards,
Sudeep

[0]: https://lore.kernel.org/r/20200211231604.GA17274@embeddedor
[1]: https://lore.kernel.org/r/20200211231252.GA14830@embeddedor
[2]: https://lore.kernel.org/r/20200211231045.GA13956@embeddedor

Re: [PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member

[Gustavo A. R. Silva]

On 2/20/20 11:18, Sudeep Holla wrote:

>>
>> [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>
> 
> Applied these 3 patches [0][1][2] for v5.7
> 

Thanks, Sudeep.
--
Gustavo