From: Herbert Xu <herbert@gondor.apana.org.au>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
Vladimir Zapolskiy <vz@mleia.com>,
Kamil Konieczny <k.konieczny@samsung.com>,
"David S. Miller" <davem@davemloft.net>,
linux-crypto@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] crypto: s5p-sss - Replace zero-length array with flexible-array member
Date: Sat, 22 Feb 2020 12:43:19 +1100 [thread overview]
Message-ID: <20200222014319.GH19028@gondor.apana.org.au> (raw)
In-Reply-To: <20200213172130.GA13395@embeddedor>
On Thu, Feb 13, 2020 at 11:21:30AM -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
> 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>
> ---
> drivers/crypto/s5p-sss.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
prev parent reply other threads:[~2020-02-22 1:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200213180724eucas1p1bb96993e9d0300cddf348d5d442f43aa@eucas1p1.samsung.com>
2020-02-13 17:21 ` [PATCH] crypto: s5p-sss - Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-14 7:09 ` Kamil Konieczny
2020-02-14 8:22 ` Krzysztof Kozlowski
2020-02-22 1:43 ` Herbert Xu [this message]
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