linux-kernel - Re: [PATCH v2] virt: tdx-guest: Handle GetQuote request error code

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Date: Mon, 15 Jan 2024 05:14:22 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "sathyanarayanan.kuppuswamy@...ux.intel.com"
	<sathyanarayanan.kuppuswamy@...ux.intel.com>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>
CC: "Williams, Dan J" <dan.j.williams@...el.com>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v2] virt: tdx-guest: Handle GetQuote request error code

Although for the failed request, output buffer length will
> be zero and can also be used by the user to identify the failure case,
> it will be more clear to return error for all failed cases.

Nit:

If I read correctly, kvmemdup() returns ZERO_SIZE_PTR if you pass the 0 size to
it, so w/o this patch it seems the kernel will report ZERO_SIZE_PTR as the
buffer to userspace.  Not sure whether this is an issue.

I guess what I want to say is, should we explicitly check quote_buf->out_len not
being 0 even the status shows success?  After all the out_len is set by the VMM.

Anyway:

Acked-by: Kai Huang <kai.huang@...el.com>


> 
> Validate the Quote data output status and return error code for all
> failed cases.
> 
> Fixes: f4738f56d1dc ("virt: tdx-guest: Add Quote generation support using TSM_REPORTS")
> Reported-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Closes: https://lore.kernel.org/linux-coco/6bdf569c-684a-4459-af7c-4430691804eb@linux.intel.com/T/#u
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
> 
> Changes since v1:
>  * Updated the commit log (Kirill)
> 
>  drivers/virt/coco/tdx-guest/tdx-guest.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c
> index 1253bf76b570..61368318fa39 100644
> --- a/drivers/virt/coco/tdx-guest/tdx-guest.c
> +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
> @@ -228,6 +228,12 @@ static int tdx_report_new(struct tsm_report *report, void *data)
>  		goto done;
>  	}
>  
> +	if (quote_buf->status != GET_QUOTE_SUCCESS) {
> +		pr_err("GetQuote request failed, ret %llx\n", quote_buf->status);
> +		ret = -EIO;
> +		goto done;
> +	}
> +
>  	buf = kvmemdup(quote_buf->data, quote_buf->out_len, GFP_KERNEL);
>  	if (!buf) {
>  		ret = -ENOMEM;