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SubjectRe: [PATCH] crypto: s5p-sss - Replace zero-length array with flexible-array member
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On 13.02.2020 18:21, 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
> 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://protect2.fireeye.com/url?k=7fbec6f4-22720d30-7fbf4dbb-0cc47a314e9a-2a4d03985644c7ed&u=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/crypto/s5p-sss.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/s5p-sss.c b/drivers/crypto/s5p-sss.c
> index d66e20a2f54c..2a16800d2579 100644
> --- a/drivers/crypto/s5p-sss.c
> +++ b/drivers/crypto/s5p-sss.c
> @@ -369,7 +369,7 @@ struct s5p_hash_reqctx {
> bool error;
>
> u32 bufcnt;
> - u8 buffer[0];
> + u8 buffer[];
> };
>
> /**
>

Looks good to me.

Acked-by: Kamil Konieczny <k.konieczny@samsung.com>

--
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland

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