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

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Date:	Mon, 29 Sep 2014 14:30:29 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, rjw@...ysocki.net
Subject: Re: [PATCH] dell-wmi: Fix access out of memory

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?

Cc: linux-acpi

> ---
> 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);
> -- 
> 1.7.9.5
> 
> 

-- 
Darren Hart
Intel Open Source Technology Center
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