linux-kernel - Re: [PATCH] cgroup: reorder flexible array members of struct cgroup

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 for Android: free password hash cracker in your pocket

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

Message-ID: <85d7f6eb-7869-551d-01b1-fa1712f4bd40@suse.de>
Date:   Sun, 22 Oct 2017 02:59:33 +1100
From:   Aleksa Sarai <asarai@...e.de>
To:     Tejun Heo <tj@...nel.org>,
        Nick Desaulniers <nick.desaulniers@...il.com>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Michael Davidson <md@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>, android-llvm@...gle.com
Subject: Re: [PATCH] cgroup: reorder flexible array members of struct
 cgroup_root

> Here, not necessarily but I don't want to move it for a bogus reason.
> Why would we disallow embedding structs with flexible members in the
> middle when it can be done and is useful?  If we want to discuss
> whether we want to avoid such usages in the kernel (but why?), sure,
> let's have that discussion but we can't decide that on "clang warns on
> it by default".

There was a talk a few years ago by the clang folks[1] saying that while 
trying to build a kernel with clang, they discovered that several places 
in the kernel uses "VLAIS" (variable Length Arrays In Structs") and 
argued that this is a violation of the C specification, despite it being 
a GNU extension. They also submitted several patches that removed this 
code (even working around a user-space visible usage of VLAIS).

[1]: 
https://www.linuxplumbersconf.org/2013/ocw/system/presentations/1221/original/VLAIS.pdf

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/