linux-kernel - Re: [PATCH 3/6] struct page: add field for vm

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Date:   Tue, 20 Feb 2018 12:54:42 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Igor Stoppa <igor.stoppa@...wei.com>
Cc:     rdunlap@...radead.org, corbet@....net, keescook@...omium.org,
        mhocko@...nel.org, labbott@...hat.com, jglisse@...hat.com,
        hch@...radead.org, cl@...ux.com,
        linux-security-module@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 3/6] struct page: add field for vm_struct

On Tue, Feb 20, 2018 at 09:53:30PM +0200, Igor Stoppa wrote:
> The patch relies on the function vmalloc_to_page ... which will return
> NULL when applied to huge mappings, while the original implementation
> will still work.

Huh?  vmalloc_to_page() should work for huge mappings...

> It was found while testing on a configuration with framebuffer.

... ah.  You tried to use vmalloc_to_page() on something which wasn't
backed by a struct page.  That's *supposed* to return NULL, but my
guess is that after this patch it returned garbage.