From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: [patch 2/2] fs, proc: Introduce the /proc/<pid>/map_files/
 directory v6
Date: Mon, 5 Sep 2011 23:20:09 +0400
Message-ID: <20110905192009.GJ761@sun>
References: <20110831075814.003575573@openvz.org>
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 <20110901080508.GF30615@sun>
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To: Vasiliy Kulikov <segoon@openwall.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, "Kirill A. Shutemov" <kirill@shutemov.name>, containers@lists.osdl.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Nathan Lynch <ntl@pobox.com>, kernel-hardening@lists.openwall.com, Oren Laadan <orenl@cs.columbia.edu>, Daniel Lezcano <dlezcano@fr.ibm.com>, Glauber Costa <glommer@parallels.com>, James Bottomley <jbottomley@parallels.com>, Tejun Heo <tj@kernel.org>, Alexey Dobriyan <adobriyan@gmail.com>, Al Viro <viro@ZenIV.linux.org.uk>, Pavel Emelyanov <xemul@parallels.com>
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On Mon, Sep 05, 2011 at 10:53:58PM +0400, Vasiliy Kulikov wrote:
...
>  
> +static int pid_no_revalidate(struct dentry *dentry, struct nameidata *nd)
> +{
> +	if (nd && nd->flags & LOOKUP_RCU)
> +		return -ECHILD;
> +
> +	d_drop(dentry);
> +	return 0;
> +}
> +

Thanks Vasiliy! So every lookup will cause dcache to drop previous cached
entry and alloc and hash new one instead, pretty dramatic, espec in case
of huge number of files mapped ;) Still since it's not time critical operation
(at least for now) I tend to agree.

	Cyrill

From mboxrd@z Thu Jan  1 00:00:00 1970
Reply-To: kernel-hardening@lists.openwall.com
Date: Mon, 5 Sep 2011 23:20:09 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
Message-ID: <20110905192009.GJ761@sun>
References: <20110831075814.003575573@openvz.org>
 <20110831080229.100652529@openvz.org>
 <20110831090612.GA3253@albatros>
 <20110831112642.GI25465@sun>
 <20110831140416.GA17626@shutemov.name>
 <20110831142622.GB30615@sun>
 <20110831151023.5b7e12da.akpm@linux-foundation.org>
 <20110901080508.GF30615@sun>
 <20110902163711.GA3124@albatros>
 <20110905185358.GA2103@albatros>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
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In-Reply-To: <20110905185358.GA2103@albatros>
Subject: [kernel-hardening] Re: [patch 2/2] fs, proc: Introduce the /proc/<pid>/map_files/
 directory v6
To: Vasiliy Kulikov <segoon@openwall.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, "Kirill A. Shutemov" <kirill@shutemov.name>, containers@lists.osdl.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Nathan Lynch <ntl@pobox.com>, kernel-hardening@lists.openwall.com, Oren Laadan <orenl@cs.columbia.edu>, Daniel Lezcano <dlezcano@fr.ibm.com>, Glauber Costa <glommer@parallels.com>, James Bottomley <jbottomley@parallels.com>, Tejun Heo <tj@kernel.org>, Alexey Dobriyan <adobriyan@gmail.com>, Al Viro <viro@ZenIV.linux.org.uk>, Pavel Emelyanov <xemul@parallels.com>
List-ID: <kernel-hardening.lists.openwall.com>

On Mon, Sep 05, 2011 at 10:53:58PM +0400, Vasiliy Kulikov wrote:
...
>  
> +static int pid_no_revalidate(struct dentry *dentry, struct nameidata *nd)
> +{
> +	if (nd && nd->flags & LOOKUP_RCU)
> +		return -ECHILD;
> +
> +	d_drop(dentry);
> +	return 0;
> +}
> +

Thanks Vasiliy! So every lookup will cause dcache to drop previous cached
entry and alloc and hash new one instead, pretty dramatic, espec in case
of huge number of files mapped ;) Still since it's not time critical operation
(at least for now) I tend to agree.

	Cyrill