linux-kernel - Re: [PATCH v2] platform/surface: aggregator: Fix access of unaligned value

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Date:   Thu, 11 Feb 2021 16:50:17 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     Mark Gross <mgross@...x.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-test-robot <lkp@...el.com>
Subject: Re: [PATCH v2] platform/surface: aggregator: Fix access of unaligned
 value

Hi,

On 2/11/21 1:41 PM, Maximilian Luz wrote:
> The raw message frame length is unaligned and explicitly marked as
> little endian. It should not be accessed without the appropriate
> accessor functions. Fix this.
> 
> Note that payload.len already contains the correct length after parsing
> via sshp_parse_frame(), so we can simply use that instead.
> 
> Reported-by: kernel-test-robot <lkp@...el.com>
> Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
> Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>

Thank you for your patch, I've applied this patch to my review-hans 
branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=review-hans

Note it will show up in my review-hans branch once I've pushed my
local branch there, which might take a while.

Once I've run some tests on this branch the patches there will be
added to the platform-drivers-x86/for-next branch and eventually
will be included in the pdx86 pull-request to Linus for the next
merge-window.

Regards,

Hans

> ---
> 
> Changes in v2:
>  - Use payload.len instead of getting the frame length directly. Note
>    that payload.len equals the frame length and is already correctly set
>    in sshp_parse_frame(), so they are exactly the same thing. Makes it
>    look a bit nicer though.
> 
>    I did drop the ACKs/Reveiewd-by in case you want to check that
>    yourselves and since that's essentially the whole change.
> 
> ---
>  drivers/platform/surface/aggregator/ssh_packet_layer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> index 583315db8b02..15d96eac6811 100644
> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> @@ -1774,7 +1774,7 @@ 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(payload.len);
>  }
>  
>  static int ssh_ptl_rx_threadfn(void *data)
>