linux-kernel - Re: [PATCH 0/4] IMA: making i_readcount a first class inode citizen

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Message-ID: <20101106104451.GC11831@ucw.cz>
Date:	Sat, 6 Nov 2010 11:44:52 +0100
From:	Pavel Machek <pavel@....cz>
To:	Eric Paris <eparis@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, hch@...radead.org,
	warthog9@...nel.org, jmorris@...ei.org, kyle@...artin.ca,
	hpa@...or.com, akpm@...ux-foundation.org, mingo@...e.hu,
	viro@...iv.linux.org.uk, Matthew Wilcox <matthew@....cx>
Subject: Re: [PATCH 0/4] IMA: making i_readcount a first class inode citizen

On Thu 2010-10-28 18:45:07, Eric Paris wrote:
> On Thu, 2010-10-28 at 15:29 -0700, Linus Torvalds wrote:
> > On Thu, Oct 28, 2010 at 3:24 PM, Dave Chinner <david@...morbit.com> wrote:
> > >
> > > Why the wrapper functions and locking? Why not an atomic variable like
> > > i_writecount?
> > 
> > Indeed. With moving this more into the VFS, let's just make sure it
> > looks like i_writecount as much as possible.
> 
> My thought was that the IMA read/write checks should happen AFTER the
> i_writecount and i_readcount counters were updated.  Thus even if we
> raced with another task we can rest assured that the other task would
> catch the situation we missed....

Is not that too late? The other process may have already acted on that data...

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