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Date: Thu, 9 Jan 2014 15:10:53 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>, Dave Chinner <david@fromorbit.com>,
        linux-fsdevel@vger.kernel.org,
        James Morris <james.l.morris@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Paul Moore <paul@paul-moore.com>, LKML <linux-kernel@vger.kernel.org>,
        Matthew Wilcox <matthew@wil.cx>, Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] vfs: Fix possible NULL pointer dereference in
 inode_permission()
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On Fri, Jan 10, 2014 at 06:41:03AM +0800, Linus Torvalds wrote:
> I think the sane short term fix is to make the kfree() of the i_security
> member be a rcu free, and not clear the member.

Interesting use case.  ;-)

							Thanx, Paul

> Not pretty, but should did this case..
> 
>      Linus
> 
> On Jan 10, 2014 6:31 AM, "Al Viro" <viro@zeniv.linux.org.uk> wrote:
> >
> > iput() definitely can sleep (that's when actual truncation and inode
> > freeing is done for opened-and-unlinked files - on the final iput() after
> > close()), but that' irrelevant here - fsnotify_delete_inode() grabs
> > a bunch of mutexes, which makes calling it from rcu callback no-go.