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From: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
To: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org,
	oleg-6lXkIZvqkOAvJsYlp49lxw@public.gmane.org
Subject: Re: [PATCH 3/20] Introduce MS_KERNMOUNT flag
Date: Mon, 13 Aug 2007 11:12:06 +0400	[thread overview]
Message-ID: <46C00446.7030703@openvz.org> (raw)
In-Reply-To: <20070811034721.GB22216-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>

Christoph Hellwig wrote:
> On Fri, Aug 10, 2007 at 03:47:55PM +0400, xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org wrote:
>> This flag tells the .get_sb callback that this is a kern_mount() call
>> so that it can trust *data pointer to be valid in-kernel one. If this
>> flag is passed from the user process, it is cleared since the *data
>> pointer is not a valid kernel object.
>>
>> Running a few steps forward - this will be needed for proc to create the
>> superblock and store a valid pid namespace on it during the namespace
>> creation. The reason, why the namespace cannot live without proc mount
>> is described in the appropriate patch.
> 
> I don't like this at all.  We should never pass kernel and userspace
> addresses through the same pointer.  Maybe add an additional argument
> to the get_sb prototype instead.  But this whole idea of mounting /proc
> from kernelspace sounds like a really bad idea to me.  /proc should
> never be mounted from the kernel but always normally from userspace.

Why then is it mounted in proc_root_init()?

Thanks,
Pavel

WARNING: multiple messages have this Message-ID (diff)
From: Pavel Emelyanov <xemul@openvz.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: akpm@osdl.org, devel@openvz.org, linux-kernel@vger.kernel.org,
	containers@lists.osdl.org, oleg@tv-sign.ru, sukadev@us.ibm.com
Subject: Re: [PATCH 3/20] Introduce MS_KERNMOUNT flag
Date: Mon, 13 Aug 2007 11:12:06 +0400	[thread overview]
Message-ID: <46C00446.7030703@openvz.org> (raw)
In-Reply-To: <20070811034721.GB22216@infradead.org>

Christoph Hellwig wrote:
> On Fri, Aug 10, 2007 at 03:47:55PM +0400, xemul@openvz.org wrote:
>> This flag tells the .get_sb callback that this is a kern_mount() call
>> so that it can trust *data pointer to be valid in-kernel one. If this
>> flag is passed from the user process, it is cleared since the *data
>> pointer is not a valid kernel object.
>>
>> Running a few steps forward - this will be needed for proc to create the
>> superblock and store a valid pid namespace on it during the namespace
>> creation. The reason, why the namespace cannot live without proc mount
>> is described in the appropriate patch.
> 
> I don't like this at all.  We should never pass kernel and userspace
> addresses through the same pointer.  Maybe add an additional argument
> to the get_sb prototype instead.  But this whole idea of mounting /proc
> from kernelspace sounds like a really bad idea to me.  /proc should
> never be mounted from the kernel but always normally from userspace.

Why then is it mounted in proc_root_init()?

Thanks,
Pavel

  parent reply	other threads:[~2007-08-13  7:12 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-10 11:47 [PATCH 3/20] Introduce MS_KERNMOUNT flag xemul-GEFAQzZX7r8dnm+yROfE0A
2007-08-10 11:47 ` xemul
2007-08-11  3:47 ` Christoph Hellwig
2007-08-11 11:22   ` Oleg Nesterov
     [not found]   ` <20070811034721.GB22216-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2007-08-13  7:12     ` Pavel Emelyanov [this message]
2007-08-13  7:12       ` Pavel Emelyanov

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