linux-kernel - Re: next-20090220: XFS, IMA: BUG: sleeping function called from invalid context at mm/slub.c:1613

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Date:	Sat, 21 Feb 2009 20:49:37 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	a.beregalov@...il.com, linux-kernel@...r.kernel.org,
	linux-next@...r.kernel.org, xfs@....sgi.com, jmorris@...ei.org,
	david safford <safford@...son.ibm.com>
Subject: Re: next-20090220: XFS, IMA: BUG: sleeping function called from
	invalid  context at mm/slub.c:1613

On Fri, 2009-02-20 at 14:28 -0800, Andrew Morton wrote: 
> On Fri, 20 Feb 2009 17:16:59 -0500
> Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> 
> > integrity: ima iint radix_tree_lookup locking fix
> > 
> > Based on Andrew Morton's comments:
> > - add missing locks around radix_tree_lookup in ima_iint_insert()
> > 
> > Signed-off-by: Mimi Zohar <zohar@...ibm.com>
> > 
> > Index: security-testing-2.6/security/integrity/ima/ima_iint.c
> > ===================================================================
> > --- security-testing-2.6.orig/security/integrity/ima/ima_iint.c
> > +++ security-testing-2.6/security/integrity/ima/ima_iint.c
> > @@ -73,8 +73,10 @@ out:
> >  	if (rc < 0) {
> >  		kmem_cache_free(iint_cache, iint);
> >  		if (rc == -EEXIST) {
> > +			spin_lock(&ima_iint_lock);
> >  			iint = radix_tree_lookup(&ima_iint_store,
> >  						 (unsigned long)inode);
> > +			spin_unlock(&ima_iint_lock);
> >  		} else
> >  			iint = NULL;
> >  	}
> 
> Can the -EEXIST ever actually happen?

> On the inode_init_always() path (at least), I don't think that any
> other thread of control can have access to this inode*, so there is no
> way in which a race can result in someone else adding this inode
> first?

True, but for those inodes which were allocated before IMA was enabled
and are being allocated in ima_iint_find_insert_get(), it could be an
issue.

> Also, idle question: why does the radix tree exist at all?  Would it
> have been possible to just add a `struct ima_iint_cache *' field to the
> inode instead?

Up until November the iint was defined directly in the inode. This
changed based on Christoph Hellwig's posting
http://lkml.org/lkml/2008/10/14/170 where he said, "bloating the inode
for this is not an option".

Mimi Zohar

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