From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35])
	by kanga.kvack.org (Postfix) with ESMTP id F0DFD9000BD
	for <linux-mm@kvack.org>; Mon, 26 Sep 2011 12:49:45 -0400 (EDT)
Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236])
	by e4.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p8QGPkXF023640
	for <linux-mm@kvack.org>; Mon, 26 Sep 2011 12:25:46 -0400
Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168])
	by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p8QGnf1F073276
	for <linux-mm@kvack.org>; Mon, 26 Sep 2011 12:49:43 -0400
Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1])
	by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p8QGnaEq020386
	for <linux-mm@kvack.org>; Mon, 26 Sep 2011 10:49:37 -0600
Date: Mon, 26 Sep 2011 22:04:26 +0530
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 17/26]   x86: arch specific hooks for
 pre/post singlestep handling.
Message-ID: <20110926163426.GA15435@linux.vnet.ibm.com>
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
References: <20110920115938.25326.93059.sendpatchset@srdronam.in.ibm.com>
 <20110920120325.25326.11641.sendpatchset@srdronam.in.ibm.com>
 <1317047033.1763.27.camel@twins>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
In-Reply-To: <1317047033.1763.27.camel@twins>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>, Linux-mm <linux-mm@kvack.org>, Arnaldo Carvalho de Melo <acme@infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Hugh Dickins <hughd@google.com>, Christoph Hellwig <hch@infradead.org>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Thomas Gleixner <tglx@linutronix.de>, Jonathan Corbet <corbet@lwn.net>, Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Roland McGrath <roland@hack.frob.com>, Andi Kleen <andi@firstfloor.org>, Andrew Morton <akpm@linux-foundation.org>

* Peter Zijlstra <peterz@infradead.org> [2011-09-26 16:23:53]:

> On Tue, 2011-09-20 at 17:33 +0530, Srikar Dronamraju wrote:
> > +fail:
> > +       pr_warn_once("uprobes: Failed to adjust return address after"
> > +               " single-stepping call instruction;"
> > +               " pid=%d, sp=%#lx\n", current->pid, sp);
> > +       return -EFAULT; 
> 
> So how can that happen? Single-Step while someone unmapped the stack?

We do a copy_to_user, copy_from_user just above this, Now if either of
them fail, we have no choice but to Bail out. What caused this EFault
may not be under Uprobes's Control.

-- 
Thanks and Regards
Srikar

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>