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Message-ID: <ec8d0f27-a3e8-3b93-6703-9935e009ceb2@redhat.com>
Date:   Wed, 14 Jun 2023 17:57:41 +0200
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Subject: Re: [PATCH 2/7] mm/hugetlb: Fix hugetlb_follow_page_mask() on
 permission checks
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To:     Peter Xu <peterx@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Matthew Wilcox <willy@infradead.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Mike Rapoport <rppt@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        James Houghton <jthoughton@google.com>,
        Hugh Dickins <hughd@google.com>
References: <20230613215346.1022773-1-peterx@redhat.com>
 <20230613215346.1022773-3-peterx@redhat.com>
 <24bc512a-b5c2-b7ea-fa83-5752cec7455b@redhat.com> <ZIng1SQ0xZ+eBua8@x1n>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <ZIng1SQ0xZ+eBua8@x1n>
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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