linux-kernel - Re: [PATCH 04/12] seq_file: Make seq_file able to access the file's opener cred

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Message-ID: <CA+55aFwhb8rFbd8xT0==+r_QV-m8ANm+0sFEqUfk9Qg4rYpm-w@mail.gmail.com>
Date:	Wed, 25 Sep 2013 17:22:51 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Djalal Harouni <tixxdz@...ndz.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>, tixxdz@...il.com
Subject: Re: [PATCH 04/12] seq_file: Make seq_file able to access the file's
 opener cred

On Wed, Sep 25, 2013 at 1:14 PM, Djalal Harouni <tixxdz@...ndz.org> wrote:
>
> Therefor add the f_cred field to the seq_file struct and a helper
> seq_f_cred() to return it.

I hate how you've split up this patch from the next one that actually
_initializes_ the new field.

The two patches should have been one.

I think the patch should also remove the 'user_ns' member, since it's
now available as f_cred->user_ns.

I also suspect that it would be better to just make the the new
seq_file member point to the 'struct file' instead. Sure, it's an
extra level of indirection, but the lifetime of f_cred is not as clear
otherwise. You don't increment the reference count, which is correct
*only* because 'seq_file' has the same lifetime as 'struct file', and
thus the reference count from struct file for the f_cred is
sufficient.

[ Time passes, I look over the other patches ]

Oh, and I note that you remove user_ns in patch 12. Again, I think
that's just splitting things up too much. It actually gets harder to
see what happens when you do this.

               Linus
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