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Date: Sat, 22 Feb 2020 12:43:12 +1100 From: Herbert Xu <herbert@...dor.apana.org.au> To: "Gustavo A. R. Silva" <gustavo@...eddedor.com> Cc: "David S. Miller" <davem@...emloft.net>, linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] crypto: img-hash - Replace zero-length array with flexible-array member On Thu, Feb 13, 2020 at 10:50:54AM -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@...eddedor.com> > --- > drivers/crypto/img-hash.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Patch applied. Thanks. -- Email: Herbert Xu <herbert@...dor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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