linux-kernel - Re: [PATCH] vfs: Fix possible NULL pointer dereference in inode

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Message-ID: <20140109231053.GP10038@linux.vnet.ibm.com>
Date:	Thu, 9 Jan 2014 15:10:53 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Dave Chinner <david@...morbit.com>,
	linux-fsdevel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	"Theodore Ts'o" <tytso@....edu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Eric Paris <eparis@...isplace.org>,
	stable <stable@...r.kernel.org>,
	Paul Moore <paul@...l-moore.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Matthew Wilcox <matthew@....cx>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] vfs: Fix possible NULL pointer dereference in
 inode_permission()

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@...iv.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.

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