linux-kernel - Re: [PATCH 4/7] mm: Introduce verify_page

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Message-ID: <202104121302.57D7EF8@keescook>
Date:   Mon, 12 Apr 2021 13:05:09 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        sstabellini@...nel.org, x86@...nel.org,
        jani.nikula@...ux.intel.com, joonas.lahtinen@...ux.intel.com,
        rodrigo.vivi@...el.com, chris@...is-wilson.co.uk,
        intel-gfx@...ts.freedesktop.org, linux-mm@...ck.org, hch@....de
Subject: Re: [PATCH 4/7] mm: Introduce verify_page_range()

On Mon, Apr 12, 2021 at 10:00:16AM +0200, Peter Zijlstra wrote:
> +struct vpr_data {
> +	int (*fn)(pte_t pte, unsigned long addr, void *data);
> +	void *data;
> +};

Eeerg. This is likely to become an attack target itself. Stored function
pointer with stored (3rd) argument.

This doesn't seem needed: only DRM uses it, and that's for error
reporting. I'd rather plumb back errors in a way to not have to add
another place in the kernel where we do func+arg stored calling.

-- 
Kees Cook