netdev - RE: [PATCH 2/4] net: make sockptr_is

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Wed, 29 Jul 2020 11:06:11 +0200 (CEST)
From:   Jan Engelhardt <jengelh@...i.de>
To:     David Laight <David.Laight@...LAB.COM>
cc:     'Christoph Hellwig' <hch@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Ido Schimmel <idosch@...sch.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 2/4] net: make sockptr_is_null strict aliasing safe


On Wednesday 2020-07-29 10:04, David Laight wrote:
>From: Christoph Hellwig <hch@....de>
>> Sent: 28 July 2020 17:39
>> 
>> While the kernel in general is not strict aliasing safe we can trivially
>> do that in sockptr_is_null without affecting code generation, so always
>> check the actually assigned union member.
>
>Even with 'strict aliasing' gcc (at least) guarantees that
>the members of a union alias each other.
>It is about the only way so safely interpret a float as an int.

The only?

  float given;
  int i;
  memcpy(&i, &given, sizeof(i));
  BUILD_BUG_ON(sizeof(i) > sizeof(given));