linux-kernel - Re: [PATCH] RFC: platform/x86: wmi: Fix check for method instance number

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Date:   Sat, 10 Jun 2017 21:15:57 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Darren Hart <dvhart@...radead.org>
Cc:     Andy Shevchenko <andy@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RFC: platform/x86: wmi: Fix check for method instance number

On Saturday 27 May 2017 13:55:34 Pali Rohár wrote:
> instance_count defines number of instances of data block and instance
> itself is indexed from zero, which means first instance has number 0.
> Therefore check for invalid instance should be non-strict inequality.
> 
> Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> ---
> I'm marking this patch as RFC because it is not tested at all and
> probably could break existing WMI drivers. Some WMI drivers pass
> instance number 1 and I'm not sure if ACPI-WMI bytecode for those
> machines has really two instances. In more cases ACPI-WMI bytecode
> does not check instance number if supports only one instance. So
> then any instance id can be used for correct execution of ACPI-WMI
> method.
> 
> So this patch is open for discussion.

Hi! Any comments?

> ---
>  drivers/platform/x86/wmi.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index cd7045f..df63037 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -191,7 +191,7 @@ acpi_status wmi_evaluate_method(const char
> *guid_string, u8 instance, if (!(block->flags & ACPI_WMI_METHOD))
>  		return AE_BAD_DATA;
> 
> -	if (block->instance_count < instance)
> +	if (block->instance_count <= instance)
>  		return AE_BAD_PARAMETER;
> 
>  	input.count = 2;
> @@ -250,7 +250,7 @@ struct acpi_buffer *out)
>  	block = &wblock->gblock;
>  	handle = wblock->handle;
> 
> -	if (block->instance_count < instance)
> +	if (block->instance_count <= instance)
>  		return AE_BAD_PARAMETER;
> 
>  	/* Check GUID is a data block */
> @@ -323,7 +323,7 @@ acpi_status wmi_set_block(const char
> *guid_string, u8 instance, block = &wblock->gblock;
>  	handle = wblock->handle;
> 
> -	if (block->instance_count < instance)
> +	if (block->instance_count <= instance)
>  		return AE_BAD_PARAMETER;
> 
>  	/* Check GUID is a data block */

-- 
Pali Rohár
pali.rohar@...il.com

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