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[2003:cb:c702:5700:cb5b:f73a:c650:1d9]) by smtp.gmail.com with ESMTPSA id m8-20020a7bca48000000b003f0373d077csm3793274wml.47.2023.04.14.02.23.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Apr 2023 02:23:57 -0700 (PDT) Message-ID: Date: Fri, 14 Apr 2023 11:23:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH 2/6] mm/hugetlb: Fix uffd-wp bit lost when unsharing happens Content-Language: en-US To: Peter Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Axel Rasmussen , Andrew Morton , Mike Kravetz , Nadav Amit , Andrea Arcangeli , linux-stable References: <20230413231120.544685-1-peterx@redhat.com> <20230413231120.544685-3-peterx@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230413231120.544685-3-peterx@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 14.04.23 01:11, Peter Xu wrote: > When we try to unshare a pinned page for a private hugetlb, uffd-wp bit can > get lost during unsharing. Fix it by carrying it over. > > This should be very rare, only if an unsharing happened on a private > hugetlb page with uffd-wp protected (e.g. in a child which shares the same > page with parent with UFFD_FEATURE_EVENT_FORK enabled). > > Cc: linux-stable > Fixes: 166f3ecc0daf ("mm/hugetlb: hook page faults for uffd write protection") > Reported-by: Mike Kravetz > Signed-off-by: Peter Xu > --- > mm/hugetlb.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 7320e64aacc6..083aae35bff8 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5637,13 +5637,16 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, > spin_lock(ptl); > ptep = hugetlb_walk(vma, haddr, huge_page_size(h)); > if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) { > + pte_t newpte = make_huge_pte(vma, &new_folio->page, !unshare); > + > /* Break COW or unshare */ > huge_ptep_clear_flush(vma, haddr, ptep); > mmu_notifier_invalidate_range(mm, range.start, range.end); > page_remove_rmap(old_page, vma, true); > hugepage_add_new_anon_rmap(new_folio, vma, haddr); > - set_huge_pte_at(mm, haddr, ptep, > - make_huge_pte(vma, &new_folio->page, !unshare)); > + if (huge_pte_uffd_wp(pte)) > + newpte = huge_pte_mkuffd_wp(newpte); > + set_huge_pte_at(mm, haddr, ptep, newpte); > folio_set_hugetlb_migratable(new_folio); > /* Make the old page be freed below */ > new_folio = page_folio(old_page); LGTM, thanks Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb