linux-kernel - Re: [PATCH] misc: fastrpc: fix improper packet size calculation

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Date:   Mon, 20 Sep 2021 13:21:44 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Jeya R <jeyr@...eaurora.org>, linux-arm-msm@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        fastrpc.upstream@....qualcomm.com
Subject: Re: [PATCH] misc: fastrpc: fix improper packet size calculation

Thanks Jeya for the fix,

On 20/09/2021 09:15, Jeya R wrote:
> The buffer list is sorted and this is not being
> considered while calculating packet size. This
> would lead to improper copy length calculation
> for non-dmaheap buffers which would eventually
> cause sending improper buffers to DSP.
> 
we need below fixes tag:

Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke method")

> Signed-off-by: Jeya R <jeyr@...eaurora.org>
> ---
>   drivers/misc/fastrpc.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index beda610..a7e550f 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -719,16 +719,21 @@ static int fastrpc_get_meta_size(struct fastrpc_invoke_ctx *ctx)
>   static u64 fastrpc_get_payload_size(struct fastrpc_invoke_ctx *ctx, int metalen)
>   {
>   	u64 size = 0;
> -	int i;
> +	int oix = 0;
Unnecessary initialization here.


>   
>   	size = ALIGN(metalen, FASTRPC_ALIGN);
> -	for (i = 0; i < ctx->nscalars; i++) {
> +	for (oix = 0; oix < ctx->nbufs; oix++) {
> +		int i = ctx->olaps[oix].raix;
> +

[--
> +		if (ctx->args[i].length == 0)
> +			continue;
> +
--]
This additional check will not really have any effect on size 
calculations, as (ctx->olaps[oix].mend - ctx->olaps[oix].mstart) would 
result in zero.
Any reason why this check was added?

--srini


>   		if (ctx->args[i].fd == 0 || ctx->args[i].fd == -1) {
>   
> -			if (ctx->olaps[i].offset == 0)
> +			if (ctx->olaps[oix].offset == 0)
>   				size = ALIGN(size, FASTRPC_ALIGN);
>   
> -			size += (ctx->olaps[i].mend - ctx->olaps[i].mstart);
> +			size += (ctx->olaps[oix].mend - ctx->olaps[oix].mstart);
>   		}
>   	}
>   
>