linux-kernel - Re: [PATCH] vfs: Tighten up linkat(..., AT_EMPTY

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Message-ID: <20130821182053.GA19624@redhat.com>
Date:	Wed, 21 Aug 2013 20:20:53 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"security@...nel.org" <security@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, Willy Tarreau <w@....eu>,
	linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	spender@...ecurity.net
Subject: Re: [PATCH] vfs: Tighten up linkat(..., AT_EMPTY_PATH)

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.

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