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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 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> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A9567100018 X-Stat-Signature: pkyzzufj43k3kfi8g3kkusjs17rhjpws X-HE-Tag: 1681464241-741470 X-HE-Meta: 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 rfNoS8G8 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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