linux-kernel - Re: [PATCH v2 5/5] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}

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Date:   Mon, 14 Aug 2023 13:21:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-coco@...ts.linux.dev, Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Dionna Glaze <dionnaglaze@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] virt: sevguest: Add TSM_REPORTS support for
 SNP_{GET, GET_EXT}_REPORT

On Mon, Aug 14, 2023 at 12:43:38AM -0700, Dan Williams wrote:
> +static u8 *sev_report_new(struct device *dev, const struct tsm_desc *desc,

> +			  size_t *outblob_len)
> +{

> +
> +	u8 *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
> +

> +
> +	*outblob_len = size;
> +	no_free_ptr(buf);
> +	return buf;

This seems broken, no_free_ptr(x) is basically xchg(X, NULL) (except no
atomics). So the above would end up being:

	return NULL;

What you want to write is somehting like:

	return no_free_ptr(buf);

or, a convenient shorthand:

	return_ptr(buf);