To: penguin-kernel@i-love.sakura.ne.jp
CC: viro@ZenIV.linux.org.uk, hch@lst.de, linux-fsdevel@vger.kernel.org,
       linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
In-reply-to: <200901060322.n063MBOt046756@www262.sakura.ne.jp> (message from
	Tetsuo Handa on Tue, 06 Jan 2009 12:22:11 +0900)
Subject: Re: [PATCH] Introduce d_realpath().
References: <200901060322.n063MBOt046756@www262.sakura.ne.jp>
Message-Id: <E1LKIeB-0006qv-Bv@pomaz-ex.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Tue, 06 Jan 2009 21:35:31 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1470
Lines: 39

On Tue, 06 Jan 2009, Tetsuo Handa wrote:
> Al, thank you very much for processing security_path_*() patch.
> Now James is reviewing our patch and he suggested
> following parts need your acknowledgments.
> Will you review and ACK for introducing a variant of d_path()?
> 
> --------------------
> Subject: Introduce d_realpath().
> 
> To remove factors that make pathname based access control difficult
> (e.g. symbolic links, "..", "//", chroot() etc.), a variant of d_path()
> which traverses up to the root of the namespace is needed.
> 
> This patch introduces d_realpath(), a variant of d_path().
> While d_path() stops traversing at current->fs->root,
> d_realpath() doesn't stop traversiong at current->fs->root.
> 
> Three differences compared to d_path().
> (1) Ignores current process's root directory.

I'd suggest calling __d_path() and passing in the namespace root
instead of the process root.  That would be a lot simpler and result
in less code duplication.

> (2) Trailing '/' is added if the pathname refers to a directory.

Caller can do this.

> (3) /proc/PID/ is represented as /proc/self/ if PID equals current->tgid.

This too.  Such hacks really don't belong in generic VFS functions.

Thanks,
Miklos
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