[PATCH] platform/surface: aggregator: Fix access of unaligned value

[PATCH] platform/surface: aggregator: Fix access of unaligned value

[Maximilian Luz]

The raw message frame length is unaligned and explicitly marked as
little endian. It should not be accessed without the appropriatte
accessor functions. Fix this.

Reported-by: kernel-test-robot <lkp@intel.com>
Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---
 drivers/platform/surface/aggregator/ssh_packet_layer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
index 583315db8b02..9a78188d8d1c 100644
--- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
+++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
@@ -1774,7 +1774,8 @@ static size_t ssh_ptl_rx_eval(struct ssh_ptl *ptl, struct ssam_span *source)
 		break;
 	}
 
-	return aligned.ptr - source->ptr + SSH_MESSAGE_LENGTH(frame->len);
+	return aligned.ptr - source->ptr
+		+ SSH_MESSAGE_LENGTH(get_unaligned_le16(&frame->len));
 }
 
 static int ssh_ptl_rx_threadfn(void *data)
-- 
2.30.0

Re: [PATCH] platform/surface: aggregator: Fix access of unaligned value

[mark gross]

Acked-by: Mark Gross <mgross@linx.intel.com>

On Thu, Feb 11, 2021 at 12:04:11AM +0100, Maximilian Luz wrote:
> The raw message frame length is unaligned and explicitly marked as
> little endian. It should not be accessed without the appropriatte
> accessor functions. Fix this.
> 
> Reported-by: kernel-test-robot <lkp@intel.com>
> Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
> ---
>  drivers/platform/surface/aggregator/ssh_packet_layer.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> index 583315db8b02..9a78188d8d1c 100644
> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> @@ -1774,7 +1774,8 @@ static size_t ssh_ptl_rx_eval(struct ssh_ptl *ptl, struct ssam_span *source)
>  		break;
>  	}
>  
> -	return aligned.ptr - source->ptr + SSH_MESSAGE_LENGTH(frame->len);
> +	return aligned.ptr - source->ptr
> +		+ SSH_MESSAGE_LENGTH(get_unaligned_le16(&frame->len));
>  }
>  
>  static int ssh_ptl_rx_threadfn(void *data)
> -- 
> 2.30.0
> 

Re: [PATCH] platform/surface: aggregator: Fix access of unaligned value

[Andy Shevchenko]

On Thu, Feb 11, 2021 at 12:04:11AM +0100, Maximilian Luz wrote:
> The raw message frame length is unaligned and explicitly marked as
> little endian. It should not be accessed without the appropriatte
> accessor functions. Fix this.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Though a few nit-picks below.

> Reported-by: kernel-test-robot <lkp@intel.com>
> Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
> ---
>  drivers/platform/surface/aggregator/ssh_packet_layer.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> index 583315db8b02..9a78188d8d1c 100644
> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> @@ -1774,7 +1774,8 @@ static size_t ssh_ptl_rx_eval(struct ssh_ptl *ptl, struct ssam_span *source)
>  		break;
>  	}
>  
> -	return aligned.ptr - source->ptr + SSH_MESSAGE_LENGTH(frame->len);
> +	return aligned.ptr - source->ptr
> +		+ SSH_MESSAGE_LENGTH(get_unaligned_le16(&frame->len));

I would leave + on previous line.
Also it's possible to annotate temporary variable and use it, but it seems not
worth to do.

Side question: Do you think the below is correct (& operator)?

        sp.len = get_unaligned_le16(&((struct ssh_frame *)sf.ptr)->len);

To me seems like you take an address to len member rather its value.

>  }
>  
>  static int ssh_ptl_rx_threadfn(void *data)

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] platform/surface: aggregator: Fix access of unaligned value

[Maximilian Luz]

On 2/11/21 11:22 AM, Andy Shevchenko wrote:
> On Thu, Feb 11, 2021 at 12:04:11AM +0100, Maximilian Luz wrote:
>> The raw message frame length is unaligned and explicitly marked as
>> little endian. It should not be accessed without the appropriatte
>> accessor functions. Fix this.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Though a few nit-picks below.
> 
>> Reported-by: kernel-test-robot <lkp@intel.com>
>> Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
>> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
>> ---
>>   drivers/platform/surface/aggregator/ssh_packet_layer.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
>> index 583315db8b02..9a78188d8d1c 100644
>> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
>> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
>> @@ -1774,7 +1774,8 @@ static size_t ssh_ptl_rx_eval(struct ssh_ptl *ptl, struct ssam_span *source)
>>   		break;
>>   	}
>>   
>> -	return aligned.ptr - source->ptr + SSH_MESSAGE_LENGTH(frame->len);
>> +	return aligned.ptr - source->ptr
>> +		+ SSH_MESSAGE_LENGTH(get_unaligned_le16(&frame->len));
> 
> I would leave + on previous line.

I can fix that if it bugs you.

> Also it's possible to annotate temporary variable and use it, but it seems not
> worth to do.

Now that you mention it, we already have the correct frame length in
payload.len. Let me draft up a new patch with that.

> Side question: Do you think the below is correct (& operator)?
> 
>          sp.len = get_unaligned_le16(&((struct ssh_frame *)sf.ptr)->len);
> 
> To me seems like you take an address to len member rather its value.

That's the point though, no? The signature is

         u16 get_unaligned_le16(const void *p)

so we do want a pointer to the len member. So I believe that is correct.

> 
>>   }
>>   
>>   static int ssh_ptl_rx_threadfn(void *data)
> 

Re: [PATCH] platform/surface: aggregator: Fix access of unaligned value

[Andy Shevchenko]

On Thu, Feb 11, 2021 at 12:58:48PM +0100, Maximilian Luz wrote:
> On 2/11/21 11:22 AM, Andy Shevchenko wrote:
> > On Thu, Feb 11, 2021 at 12:04:11AM +0100, Maximilian Luz wrote:
> > > The raw message frame length is unaligned and explicitly marked as
> > > little endian. It should not be accessed without the appropriatte
> > > accessor functions. Fix this.

...

> > Also it's possible to annotate temporary variable and use it, but it seems not
> > worth to do.
> 
> Now that you mention it, we already have the correct frame length in
> payload.len. Let me draft up a new patch with that.

Good!

> > Side question: Do you think the below is correct (& operator)?
> > 
> >          sp.len = get_unaligned_le16(&((struct ssh_frame *)sf.ptr)->len);
> > 
> > To me seems like you take an address to len member rather its value.
> 
> That's the point though, no? The signature is
> 
>         u16 get_unaligned_le16(const void *p)
> 
> so we do want a pointer to the len member. So I believe that is correct.

Indeed. I messed up with le16_to_cpu().

-- 
With Best Regards,
Andy Shevchenko