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

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Message-ID: <c4c805ed-5869-81c2-4c05-cf53bfbef168@huawei.com>
Date:   Wed, 21 Feb 2018 14:01:20 +0200
From:   Igor Stoppa <igor.stoppa@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
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 20/02/18 22:54, Matthew Wilcox wrote:
> On Tue, Feb 20, 2018 at 09:53:30PM +0200, Igor Stoppa wrote:

[...]

>> 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.

it seems to return garbage also without this patch, but I need to clean
up the code, try it again and possibly come up with a demo patch for
triggering the problem.

I'll investigate it more. However it doesn't seem to be related to the
functionality I need. So I plan to treat it as separate issue and leave
find_vm_area untouched, at least in pmalloc scope.

--
igor