Re: [PATCH] cxl/mbox: Fix missing variable payload checks in cmd size validation

[Alison Schofield <alison.schofield@intel.com>]

On Tue, Jun 28, 2022 at 01:04:27PM -0700, Vishal Verma wrote:
> The conversion of command sizes to unsigned missed a couple of checks
> against variable size payloads during command validation, which made all
> variable payload commands unconditionally fail. Add the checks back using
> the new CXL_VARIABLE_PAYLOAD scheme.
> 
> Reported-by: Abhi Cs <abhi.cs@intel.com>
> Fixes: 26f89535a5bb ("cxl/mbox: Use type __u32 for mailbox payload sizes")
> Cc: <stable@vger.kernel.org>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Alison Schofield <alison.schofield@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

with one caveat below...
Reviewed-by: Alison Schofield <alison.schofield@intel.com>


> ---
>  drivers/cxl/core/mbox.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 40e3ccb2bf3e..d929b89d12a7 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -355,12 +355,14 @@ static int cxl_to_mem_cmd(struct cxl_mem_command *mem_cmd,
>  		return -EBUSY;
>  
>  	/* Check the input buffer is the expected size */
> -	if (info->size_in != send_cmd->in.size)
> -		return -ENOMEM;
> +	if (info->size_in != CXL_VARIABLE_PAYLOAD)
> +		if (info->size_in != send_cmd->in.size)
> +			return -ENOMEM;

We can leave it to Dan to arbitrate, but I don't think nested
if's without brackets follow kernel coding style.

However, Dan didn't like my nested if's with brackets either.
He'd prefer using &&

>  
>  	/* Check the output buffer is at least large enough */
> -	if (send_cmd->out.size < info->size_out)
> -		return -ENOMEM;
> +	if (info->size_out != CXL_VARIABLE_PAYLOAD)
> +		if (send_cmd->out.size < info->size_out)
> +			return -ENOMEM;
>  
>  	*mem_cmd = (struct cxl_mem_command) {
>  		.info = {
> 
> base-commit: 1985cf58850562e4b960e19d46f0d8f19d6c7cbd
> -- 
> 2.36.1
>