linux-kernel - Re: [PATCH 2/7] mm/hugetlb: Fix hugetlb_follow_page

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Message-ID: <ec8d0f27-a3e8-3b93-6703-9935e009ceb2@redhat.com>
Date:   Wed, 14 Jun 2023 17:57:41 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Matthew Wilcox <willy@...radead.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Rapoport <rppt@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        James Houghton <jthoughton@...gle.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 2/7] mm/hugetlb: Fix hugetlb_follow_page_mask() on
 permission checks

On 14.06.23 17:46, Peter Xu wrote:
> On Wed, Jun 14, 2023 at 05:31:36PM +0200, David Hildenbrand wrote:
>> On 13.06.23 23:53, Peter Xu wrote:
>>> It seems hugetlb_follow_page_mask() was missing permission checks.  For
>>> example, one follow_page() can get the hugetlb page with FOLL_WRITE even if
>>> the page is read-only.
>>
>> I'm curious if there even is a follow_page() user that operates on hugetlb
>> ...
>>
>> s390x secure storage does not apply to hugetlb IIRC.
> 
> You're the expert, so I'll rely on you. :)
> 

Hehe, there is a comment in gmap_destroy_page(), above one of the 
follow_page() users:

	/*
	 * Huge pages should not be able to become secure
	 */
	if (is_vm_hugetlb_page(vma))
		goto out;


-- 
Cheers,

David / dhildenb