From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH] vfs: Tighten up linkat(..., AT_EMPTY_PATH)
Date: Wed, 21 Aug 2013 20:20:53 +0200
Message-ID: <20130821182053.GA19624@redhat.com>
References: <CALCETrXMQdjRyvP8RHOd5xjciurS7-hKUOExvkvQ1RWmdRdypA@mail.gmail.com> <0be9da18c0ca360773a397de3063d01019ff88d8.1377107508.git.luto@amacapital.net>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	"security@kernel.org" <security@kernel.org>,
	Ingo Molnar <mingo@kernel.org>, Willy Tarreau <w@1wt.eu>,
	linux-kernel@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	spender@grsecurity.net
To: Andy Lutomirski <luto@amacapital.net>
Return-path: <linux-kernel-owner@vger.kernel.org>
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In-Reply-To: <0be9da18c0ca360773a397de3063d01019ff88d8.1377107508.git.luto@amacapital.net>
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Can't really comment the patch, just a nit:

On 08/21, Andy Lutomirski wrote:
>
> +static bool may_flink(const struct path *path)
> +{
> +	bool ret;
> +	struct inode *inode = path->dentry->d_inode;
> +
> +	/*
> +	 * This is racy: I_LINKABLE could be cleared between this check
> +	 * and the actual link operation.

OK,

> +	spin_lock(&inode->i_lock);
> +	ret = !!(inode->i_state & I_LINKABLE);
> +	spin_unlock(&inode->i_lock);

so why do we need to take a lock ?

Oleg.