linux-kernel - Re: [PATCH v5 3.1.0-rc4-tip 1/26] uprobes: Auxillary routines to insert, find, delete uprobes

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Date:	Mon, 26 Sep 2011 17:29:19 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 1/26]   uprobes: Auxillary routines to
 insert, find, delete uprobes

* Peter Zijlstra <peterz@...radead.org> [2011-09-26 13:18:38]:

> On Tue, 2011-09-20 at 16:42 +0100, Stefan Hajnoczi wrote:
> > On Tue, Sep 20, 2011 at 05:29:49PM +0530, Srikar Dronamraju wrote:
> > > +static void delete_uprobe(struct uprobe *uprobe)
> > > +{
> > > +	unsigned long flags;
> > > +
> > > +	spin_lock_irqsave(&uprobes_treelock, flags);
> > > +	rb_erase(&uprobe->rb_node, &uprobes_tree);
> > > +	spin_unlock_irqrestore(&uprobes_treelock, flags);
> > > +	put_uprobe(uprobe);
> > > +	iput(uprobe->inode);
> > 
> > Use-after-free when put_uprobe() kfrees() the uprobe?
> 
> I suspect the caller still has one, and this was the reference for being
> part of the tree. But yes, that could do with a comment.
> 

Yes, the caller has a reference, However I went ahead and changed the
order of the last two statements.

> The comment near atomic_set() in __insert_uprobe() isn't too clear
> either. /* get access + drop ref */, would naively seem +1 -1 = 0,
> instead of +1 +1 = 2.
> 

Okay, Have modified the comment to /* get access + creation ref */

-- 
Thanks and Regards
Srikar
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