linux-kernel - Re: [PATCH] dell-wmi: Fix access out of memory

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Message-ID: <3073358.myrKz9QbdW@vostro.rjw.lan>
Date:	Tue, 30 Sep 2014 01:26:03 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Darren Hart <dvhart@...radead.org>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH] dell-wmi: Fix access out of memory

On Monday, September 29, 2014 02:30:29 PM Darren Hart wrote:
> On Mon, Sep 29, 2014 at 03:10:51PM +0200, Pali Rohár wrote:
> > Without this patch driver dell-wmi is trying to access elements of dynamically
> > allocated array without checking array size. This can lead to memory corruption
> > or kernel panic. This patch adds missing checks for array size.
> > 
> > Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> 
> Looks good to me. Rafael, any concerns?

Not anything obvious.

> 
> Cc: linux-acpi

Thanks!


> > ---
> > This patch should be probably applied to stable kernel trees as it fixing
> > possible memory corruption.
> > ---
> >  drivers/platform/x86/dell-wmi.c |   12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
> > index 390e8e3..25721bf 100644
> > --- a/drivers/platform/x86/dell-wmi.c
> > +++ b/drivers/platform/x86/dell-wmi.c
> > @@ -163,18 +163,24 @@ static void dell_wmi_notify(u32 value, void *context)
> >  		const struct key_entry *key;
> >  		int reported_key;
> >  		u16 *buffer_entry = (u16 *)obj->buffer.pointer;
> > +		int buffer_size = obj->buffer.length/2;
> >  
> > -		if (dell_new_hk_type && (buffer_entry[1] != 0x10)) {
> > +		if (buffer_size >= 2 && dell_new_hk_type && buffer_entry[1] != 0x10) {
> >  			pr_info("Received unknown WMI event (0x%x)\n",
> >  				buffer_entry[1]);
> >  			kfree(obj);
> >  			return;
> >  		}
> >  
> > -		if (dell_new_hk_type || buffer_entry[1] == 0x0)
> > +		if (buffer_size >= 3 && (dell_new_hk_type || buffer_entry[1] == 0x0))
> >  			reported_key = (int)buffer_entry[2];
> > -		else
> > +		else if (buffer_size >= 2)
> >  			reported_key = (int)buffer_entry[1] & 0xffff;
> > +		else {
> > +			pr_info("Received unknown WMI event\n");
> > +			kfree(obj);
> > +			return;
> > +		}
> >  
> >  		key = sparse_keymap_entry_from_scancode(dell_wmi_input_dev,
> >  							reported_key);
> 
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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