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From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Miller <davem@davemloft.net>,
	mhiramat@redhat.com,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kprobes: disable preempt for module_text_address()
Date: Tue, 4 Nov 2008 19:58:24 +0530	[thread overview]
Message-ID: <20081104142824.GA24326@in.ibm.com> (raw)
In-Reply-To: <490FE405.1000105@cn.fujitsu.com>

On Tue, Nov 04, 2008 at 01:56:21PM +0800, Lai Jiangshan wrote:
> 
> __register_kprobe() may be preempted after module_text_address()
> but before try_module_get(), and in this interval the module may be
> unloaded and try_module_get(probed_mod) will access to invalid address.
> this patch uses preempt_disable() to protect it.

Looking at other users of try_module_get, I don't see this as a usage
model being followed elsewhere. Also, in case such a preemption does
happen, module_is_live() will fail and we should still be ok.

I don't see a reason for this patch unless there is a clear failure case
(register_kprobe failing 'cos of a module unload is perfectly ok).

Ananth

  reply	other threads:[~2008-11-04 14:29 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-04  5:56 Lai Jiangshan
2008-11-04 14:28 ` Ananth N Mavinakayanahalli [this message]
2008-11-05  0:53   ` Lai Jiangshan
2008-11-05  1:27 ` Masami Hiramatsu
2008-11-05  1:47   ` Lai Jiangshan
2008-11-05 19:30     ` Hiroshi Shimamoto
2008-11-05 21:40     ` Masami Hiramatsu
2008-11-05 22:46       ` Hiroshi Shimamoto
2008-11-05 23:07         ` Masami Hiramatsu
2008-11-06  0:06           ` [PATCH] kprobes: bugfix: try_module_get even if calling_mod is NULL Masami Hiramatsu
2008-11-07  1:00             ` Andrew Morton
2008-11-07  2:28               ` Masami Hiramatsu
2008-11-07  2:54                 ` Andrew Morton
2008-11-07  4:46                   ` Ananth N Mavinakayanahalli
2008-11-06  1:06       ` [PATCH] kprobes: disable preempt for module_text_address() Lai Jiangshan
2008-11-06 15:37         ` [PATCH] kprobes: disable preempt for module_text_address() and kernel_text_address() Masami Hiramatsu
2008-11-07  0:32           ` Lai Jiangshan

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