From: Kees Cook <keescook@chromium.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: linux-security-module <linux-security-module@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Casey Schaufler <casey@schaufler-ca.com>,
Christoph Hellwig <hch@infradead.org>,
Igor Stoppa <igor.stoppa@huawei.com>,
James Morris <james.l.morris@oracle.com>,
Paul Moore <paul@paul-moore.com>,
Stephen Smalley <sds@tycho.nsa.gov>
Subject: Re: [PATCH v2] LSM: Convert security_hook_heads into explicit array of struct list_head
Date: Sun, 28 May 2017 14:19:22 -0700 [thread overview]
Message-ID: <CAGXu5jK2azpWLOg=EGEOhPySN52_JpMcXoWaSkNSZhxF1_dNFA@mail.gmail.com> (raw)
In-Reply-To: <1496003387-3184-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
On Sun, May 28, 2017 at 1:29 PM, Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
> Commit 3dfc9b02864b19f4 ("LSM: Initialize security_hook_heads upon
> registration.") treats "struct security_hook_heads" as an implicit array
> of "struct list_head" so that we can eliminate code for static
> initialization. Although we haven't encountered compilers which do not
> treat sizeof(security_hook_heads) != sizeof(struct list_head) *
> (sizeof(security_hook_heads) / sizeof(struct list_head)), Casey does not
> like the assumption that a structure of N elements can be assumed to be
> the same as an array of N elements.
>
> Now that Kees found that randstruct complains about such casting
>
> security/security.c: In function 'security_init':
> security/security.c:59:20: note: found mismatched op0 struct pointer types: 'struct list_head' and 'struct security_hook_heads'
>
> struct list_head *list = (struct list_head *) &security_hook_heads;
>
> and Christoph thinks that we should fix it rather than make randstruct
> whitelist it, this patch fixes it.
>
> It would be possible to revert commit 3dfc9b02864b19f4, but this patch
> converts security_hook_heads into an explicit array of struct list_head
> by introducing an enum, due to reasons explained below.
>
> Igor proposed a sealable memory allocator, and the LSM hooks
> ("struct security_hook_heads security_hook_heads" and
> "struct security_hook_list ...[]") will benefit from that allocator via
> protection using set_memory_ro()/set_memory_rw(), and that allocator
> will remove CONFIG_SECURITY_WRITABLE_HOOKS config option. Thus, we will
> likely be moving to that direction.
>
> This means that these structures will be allocated at run time using
> that allocator, and therefore the address of these structures will be
> determined at run time rather than compile time.
>
> But currently, LSM_HOOK_INIT() macro depends on the address of
> security_hook_heads being known at compile time. If we use an enum
> so that LSM_HOOK_INIT() macro does not need to know absolute address of
> security_hook_heads, it will help us to use that allocator for LSM hooks.
>
> As a result of introducing an enum, security_hook_heads becomes a local
> variable. In order to pass 80 columns check by scripts/checkpatch.pl ,
> rename security_hook_heads to hook_heads.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: Stephen Smalley <sds@tycho.nsa.gov>
> Cc: Casey Schaufler <casey@schaufler-ca.com>
> Cc: James Morris <james.l.morris@oracle.com>
> Cc: Igor Stoppa <igor.stoppa@huawei.com>
> Cc: Christoph Hellwig <hch@infradead.org>
Looks good to me; thanks for persisting! :)
Acked-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2017-05-28 21:19 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-27 11:17 [PATCH] LSM: Convert security_hook_heads into explicit array of struct list_head Tetsuo Handa
2017-05-27 22:30 ` Casey Schaufler
2017-05-28 0:38 ` Tetsuo Handa
2017-05-28 1:04 ` Kees Cook
2017-05-28 1:26 ` Tetsuo Handa
2017-05-28 17:57 ` Casey Schaufler
2017-05-30 10:22 ` James Morris
2017-05-30 14:29 ` Tetsuo Handa
2017-05-30 15:25 ` Alan Cox
2017-05-30 23:06 ` James Morris
2017-05-31 10:41 ` Tetsuo Handa
2017-05-31 11:04 ` James Morris
2017-05-31 11:31 ` Tetsuo Handa
2017-05-31 14:43 ` Alan Cox
2017-05-31 15:10 ` Tetsuo Handa
2017-05-31 15:14 ` Alan Cox
2017-05-31 9:44 ` José Bollo
2017-05-28 20:29 ` [PATCH v2] " Tetsuo Handa
2017-05-28 21:19 ` Kees Cook [this message]
2017-05-29 17:32 ` Casey Schaufler
2017-05-30 10:32 ` James Morris
2017-05-31 20:49 ` Igor Stoppa
2017-05-31 22:56 ` James Morris
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAGXu5jK2azpWLOg=EGEOhPySN52_JpMcXoWaSkNSZhxF1_dNFA@mail.gmail.com' \
--to=keescook@chromium.org \
--cc=casey@schaufler-ca.com \
--cc=hch@infradead.org \
--cc=igor.stoppa@huawei.com \
--cc=james.l.morris@oracle.com \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=paul@paul-moore.com \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=sds@tycho.nsa.gov \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).