From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: "Horia Geanta" <horia.geanta@nxp.com>,
"Aymen Sghaier" <aymen.sghaier@nxp.com>,
"Herbert Xu" <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
"Atul Gupta" <atul.gupta@chelsio.com>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"Breno Leitão" <leitao@debian.org>,
"Nayna Jain" <nayna@linux.ibm.com>,
"Paulo Flabiano Smorigo" <pfsmorigo@gmail.com>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Paul Mackerras" <paulus@samba.org>,
"Michael Ellerman" <mpe@ellerman.id.au>
Cc: "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-mediatek@lists.infradead.org"
<linux-mediatek@lists.infradead.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] crypto: Replace zero-length array with flexible-array member
Date: Tue, 25 Feb 2020 08:00:58 -0600 [thread overview]
Message-ID: <1d4ae159-f45b-e12d-1fa1-e7671f76fefc@embeddedor.com> (raw)
In-Reply-To: <VI1PR0402MB3485175AB5B3092409DC26AA98ED0@VI1PR0402MB3485.eurprd04.prod.outlook.com>
On 2/25/20 07:44, Horia Geanta wrote:
> On 2/24/2020 6:18 PM, 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>
> Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
>
Thank you, Horia.
--
Gustavo
> for caam driver:
>
>> drivers/crypto/caam/caamalg.c | 2 +-
>> drivers/crypto/caam/caamalg_qi.c | 4 ++--
>> drivers/crypto/caam/caamalg_qi2.h | 6 +++---
>> drivers/crypto/caam/caamhash.c | 2 +-
>
> Thanks,
> Horia
>
next prev parent reply other threads:[~2020-02-25 15:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-24 16:21 [PATCH] crypto: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-25 13:44 ` Horia Geanta
2020-02-25 14:00 ` Gustavo A. R. Silva [this message]
2020-03-06 1:48 ` Herbert Xu
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