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[209.132.183.28]) by mx.google.com with ESMTPS id e19si2453317qvf.126.2019.04.22.12.53.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Apr 2019 12:53:10 -0700 (PDT) Received-SPF: pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 669C7CA1DF; Mon, 22 Apr 2019 19:53:09 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.236]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BA92F10816BC; Mon, 22 Apr 2019 19:53:05 +0000 (UTC) Date: Mon, 22 Apr 2019 15:53:04 -0400 From: Jerome Glisse To: Laurent Dufour Cc: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , aneesh.kumar@linux.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , sergey.senozhatsky.work@gmail.com, Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, Daniel Jordan , David Rientjes , Ganesh Mahendran , Minchan Kim , Punit Agrawal , vinayak menon , Yang Shi , zhong jiang , Haiyan Song , Balbir Singh , sj38.park@gmail.com, Michel Lespinasse , Mike Rapoport , linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [PATCH v12 12/31] mm: protect SPF handler against anon_vma changes Message-ID: <20190422195303.GC14666@redhat.com> References: <20190416134522.17540-1-ldufour@linux.ibm.com> <20190416134522.17540-13-ldufour@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190416134522.17540-13-ldufour@linux.ibm.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 22 Apr 2019 19:53:09 +0000 (UTC) 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 Tue, Apr 16, 2019 at 03:45:03PM +0200, Laurent Dufour wrote: > The speculative page fault handler must be protected against anon_vma > changes. This is because page_add_new_anon_rmap() is called during the > speculative path. > > In addition, don't try speculative page fault if the VMA don't have an > anon_vma structure allocated because its allocation should be > protected by the mmap_sem. > > In __vma_adjust() when importer->anon_vma is set, there is no need to > protect against speculative page faults since speculative page fault > is aborted if the vma->anon_vma is not set. > > When calling page_add_new_anon_rmap() vma->anon_vma is necessarily > valid since we checked for it when locking the pte and the anon_vma is > removed once the pte is unlocked. So even if the speculative page > fault handler is running concurrently with do_unmap(), as the pte is > locked in unmap_region() - through unmap_vmas() - and the anon_vma > unlinked later, because we check for the vma sequence counter which is > updated in unmap_page_range() before locking the pte, and then in > free_pgtables() so when locking the pte the change will be detected. > > Signed-off-by: Laurent Dufour Reviewed-by: Jérôme Glisse > --- > mm/memory.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 423fa8ea0569..2cf7b6185daa 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -377,7 +377,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma, > * Hide vma from rmap and truncate_pagecache before freeing > * pgtables > */ > + vm_write_begin(vma); > unlink_anon_vmas(vma); > + vm_write_end(vma); > unlink_file_vma(vma); > > if (is_vm_hugetlb_page(vma)) { > @@ -391,7 +393,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma, > && !is_vm_hugetlb_page(next)) { > vma = next; > next = vma->vm_next; > + vm_write_begin(vma); > unlink_anon_vmas(vma); > + vm_write_end(vma); > unlink_file_vma(vma); > } > free_pgd_range(tlb, addr, vma->vm_end, > -- > 2.21.0 >