linux-kernel - [PATCH] kprobes: bugfix: try_module_get even if calling

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Date:	Wed, 05 Nov 2008 19:06:57 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>, ananth@...ibm.com
CC:	Lai Jiangshan <laijs@...fujitsu.com>,
	David Miller <davem@...emloft.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] kprobes: bugfix: try_module_get even if calling_mod is NULL

Get probed module even if the caller is in the kernel core code.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
---

>> One question, off topic.
>> If calling_mod is NULL, no try_module_get(), is that OK?
>
> Good question. Currently, kprobes is called only from kernel modules,
> so calling_mod should be always !NULL.
> However, it should be fixed, because the logic is not correct.

Thank you so much. So here is the additional bugfix patch.

 kernel/kprobes.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: 2.6.28-rc3/kernel/kprobes.c
===================================================================
--- 2.6.28-rc3.orig/kernel/kprobes.c
+++ 2.6.28-rc3/kernel/kprobes.c
@@ -634,7 +634,7 @@ static int __kprobes __register_kprobe(s
 		 * avoid incrementing the module refcount, so as to allow
 		 * unloading of self probing modules.
 		 */
-		if (calling_mod && calling_mod != probed_mod) {
+		if (calling_mod != probed_mod) {
 			if (unlikely(!try_module_get(probed_mod))) {
 				preempt_enable();
 				return -EINVAL;

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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