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Message-ID: <CAHmME9rp2oSCo0eu92jKm00S0eJHz65bJKXRpeS7=_EV6zZNYw@mail.gmail.com>
Date: Wed, 14 Dec 2016 20:38:06 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc: David Miller <davem@...emloft.net>, David Laight <David.Laight@...lab.com>,
Netdev <netdev@...r.kernel.org>, kernel-hardening@...ts.openwall.com,
Andi Kleen <ak@...ux.intel.com>, LKML <linux-kernel@...r.kernel.org>,
Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] secure_seq: use siphash24 instead of md5_transform
Hi Hannes,
On Wed, Dec 14, 2016 at 8:22 PM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> I don't think this helps. Did you test it? I don't see reason why
> padding could be left out between `d' and `end' because of the flexible
> array member?
Because the type u8 doesn't require any alignment requirements, it can
nestle right up there cozy with the u16:
zx2c4@...nkpad ~ $ cat a.c
#include <stdint.h>
#include <stdio.h>
#include <stddef.h>
int main()
{
struct {
uint64_t a;
uint32_t b;
uint32_t c;
uint16_t d;
char x[];
} a;
printf("%zu\n", sizeof(a));
printf("%zu\n", offsetof(typeof(a), x));
return 0;
}
zx2c4@...nkpad ~ $ gcc a.c
zx2c4@...nkpad ~ $ ./a.out
24
18
Jason
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