linux-kernel - Re: flex_array related problems on selinux policy loading

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Message-ID: <20110131080826.GJ3070@secunet.com>
Date:	Mon, 31 Jan 2011 09:08:26 +0100
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	Eric Paris <eparis@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: flex_array related problems on selinux policy loading

On Wed, Jan 26, 2011 at 08:10:16AM -0800, Dave Hansen wrote:
> 
> > If we would make
> > flex_array of dynamic size, say metadata plus the maximum size of the array
> > in the case that the metadata and the array fit into a single page, and
> > metadata plus space for all the base pointers we need to dereference the
> > parts, if the metadata and array is beyond page size. With this, the struct
> > flex_array would have a reasonable size in any case, even if the array to
> > store is small or of zero size.
> 
> Sounds like a good idea to me.  Done right, it should only really affect
> the allocation path since we use kmalloc() already, and we can still
> plain kfree() it.
> 


I started to look into making flex_array of dynamic size.
There are al lot of structural changes necessary, so I think this
is too much just to fix a zero size allocation bug. So
lets fix it like you proposed it by allocating the flex_array
in any case and accept that it will be of PAGE_SIZE by now.
Making flex_array of dynamic size can wait for 2.6.39 I think.

Steffen
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