linux-kernel - Re: [PATCH] x86/sev: get the AP jump table address from secrets page

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Message-ID: <YmBRW6xMhNiW7JRU@zn.tnic>
Date:   Wed, 20 Apr 2022 20:30:51 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Michael Roth <michael.roth@....com>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Kees Cook <keescook@...omium.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Venu Busireddy <venu.busireddy@...cle.com>,
        Joerg Roedel <jroedel@...e.de>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH] x86/sev: get the AP jump table address from secrets page

On Wed, Apr 20, 2022 at 10:27:51AM -0500, Michael Roth wrote:
> +static u64 get_secrets_page(void)
> +{
> +	u64 pa_data = boot_params.cc_blob_address;
> +	struct cc_blob_sev_info info;
> +	void *map;
> +
> +	/*
> +	 * The CC blob contains the address of the secrets page, check if the
> +	 * blob is present.
> +	 */
> +	if (!pa_data)
> +		return 0;
> +
> +	map = early_memremap(pa_data, sizeof(info));

That function can return NULL so you need to handle it.

> +	memcpy(&info, map, sizeof(info));
> +	early_memunmap(map, sizeof(info));
> +
> +	/* smoke-test the secrets page passed */
> +	if (!info.secrets_phys || info.secrets_len != PAGE_SIZE)
> +		return 0;
> +
> +	return info.secrets_phys;
> +}
> +
> +static u64 get_snp_jump_table_addr(void)
> +{
> +	struct snp_secrets_page_layout *layout;
> +	u64 pa = get_secrets_page();
> +	u64 addr;

Please don't hide the function call in the local variables declaration
but do this instead:

        struct snp_secrets_page_layout *layout;
        u64 pa, addr;

        pa = get_secrets_page();
        if (!pa)
                return 0;

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette