linux-kernel - Re: [patch 3/3] ThinkPad ACPI: fix possible NULL pointer dereference

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Message-ID: <20080418125502.GA7674@cvg>
Date:	Fri, 18 Apr 2008 16:55:02 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	bfields@...ldses.org, neilb@...e.de, ibm-acpi@....eng.br,
	len.brown@...el.com, kkeil@...e.de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 3/3] ThinkPad ACPI: fix possible NULL pointer
	dereference

[Pavel Machek - Fri, Apr 18, 2008 at 02:41:12PM +0200]
| Hi!
| 
| > Fix potential NULL pointer dereference if kstrdup failed
| > 
| > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
| > 
| > ---
| > 
| > Index: linux-2.6.git/drivers/misc/thinkpad_acpi.c
| > ===================================================================
| > --- linux-2.6.git.orig/drivers/misc/thinkpad_acpi.c	2008-04-16 20:35:34.000000000 +0400
| > +++ linux-2.6.git/drivers/misc/thinkpad_acpi.c	2008-04-16 20:36:38.000000000 +0400
| > @@ -5826,7 +5826,7 @@ static void __init get_thinkpad_model_da
| >  
| >  	tp->model_str = kstrdup(dmi_get_system_info(DMI_PRODUCT_VERSION),
| >  					GFP_KERNEL);
| > -	if (strnicmp(tp->model_str, "ThinkPad", 8) != 0) {
| > +	if (tp->model_str && strnicmp(tp->model_str, "ThinkPad", 8) != 0) {
| >  		kfree(tp->model_str);
| >  		tp->model_str = NULL;
| >  	}
| 
| are you sure? This seems to assume machine is thinkpad if kstrdup
| fails... which is very wrong.

No, it's *not* wrong, look there we have

	tp->model_str = kstrdup(dmi_get_system_info(DMI_PRODUCT_VERSION),
						GFP_KERNEL);

lets assume we've got NULL here so probe_for_thinkpad() will check for it

	is_thinkpad = (thinkpad_id.model_str != NULL);


Thanks for comment

		- Cyrill -
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