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[209.132.183.28]) by mx.google.com with ESMTPS id z7si10093001qtz.1.2019.07.24.04.37.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jul 2019 04:37:15 -0700 (PDT) Received-SPF: pass (google.com: domain of oleg@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 oleg@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 748FC30BD1B1; Wed, 24 Jul 2019 11:37:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 53FB760BCE; Wed, 24 Jul 2019 11:37:12 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 24 Jul 2019 13:37:14 +0200 (CEST) Date: Wed, 24 Jul 2019 13:37:11 +0200 From: Oleg Nesterov To: Song Liu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, matthew.wilcox@oracle.com, kirill.shutemov@linux.intel.com, peterz@infradead.org, rostedt@goodmis.org, kernel-team@fb.com, william.kucharski@oracle.com Subject: Re: [PATCH v8 2/4] uprobe: use original page when all uprobes are removed Message-ID: <20190724113711.GE21599@redhat.com> References: <20190724083600.832091-1-songliubraving@fb.com> <20190724083600.832091-3-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190724083600.832091-3-songliubraving@fb.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 24 Jul 2019 11:37:14 +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 07/24, Song Liu wrote: > > lock_page(old_page); > @@ -177,15 +180,24 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, > mmu_notifier_invalidate_range_start(&range); > err = -EAGAIN; > if (!page_vma_mapped_walk(&pvmw)) { > - mem_cgroup_cancel_charge(new_page, memcg, false); > + if (!orig) > + mem_cgroup_cancel_charge(new_page, memcg, false); > goto unlock; > } > VM_BUG_ON_PAGE(addr != pvmw.address, old_page); > > get_page(new_page); > - page_add_new_anon_rmap(new_page, vma, addr, false); > - mem_cgroup_commit_charge(new_page, memcg, false, false); > - lru_cache_add_active_or_unevictable(new_page, vma); > + if (orig) { > + lock_page(new_page); /* for page_add_file_rmap() */ > + page_add_file_rmap(new_page, false); Shouldn't we re-check new_page->mapping after lock_page() ? Or we can't race with truncate? and I am worried this code can try to lock the same page twice... Say, the probed application does MADV_DONTNEED and then writes "int3" into vma->vm_file at the same address to fool verify_opcode(). Oleg.