Re: [PATCH] crypto: Replace zero-length array with flexible-array member

Herbert Xu
2020-03-06T01:49:22Z

On Mon, Feb 24, 2020 at 10:21:00AM -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/caam/caamalg.c | 2 +-
> drivers/crypto/caam/caamalg_qi.c | 4 ++--
> drivers/crypto/caam/caamalg_qi2.h | 6 +++---
> drivers/crypto/caam/caamhash.c | 2 +-
> drivers/crypto/cavium/nitrox/nitrox_main.c | 2 +-
> drivers/crypto/chelsio/chcr_core.h | 2 +-
> drivers/crypto/mediatek/mtk-sha.c | 2 +-
> drivers/crypto/nx/nx.h | 2 +-
> drivers/crypto/omap-sham.c | 4 ++--
> include/crypto/if_alg.h | 2 +-
> 10 files changed, 14 insertions(+), 14 deletions(-)

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