From patchwork Fri Dec 4 18:19:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 11952081 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0EABC4361B for ; Fri, 4 Dec 2020 18:20:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8469F22C9C for ; Fri, 4 Dec 2020 18:20:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730088AbgLDSUl (ORCPT ); Fri, 4 Dec 2020 13:20:41 -0500 Received: from mail.kernel.org ([198.145.29.99]:45422 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729780AbgLDSUl (ORCPT ); Fri, 4 Dec 2020 13:20:41 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EE9AD22C9C; Fri, 4 Dec 2020 18:20:00 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1klFgV-00G3EZ-5G; Fri, 04 Dec 2020 18:19:59 +0000 From: Marc Zyngier To: Paolo Bonzini Cc: Keqian Zhu , Will Deacon , Yanan Wang , kernel-team@android.com, James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/3] KVM: arm64: Fix memory leak on stage2 update of a valid PTE Date: Fri, 4 Dec 2020 18:19:12 +0000 Message-Id: <20201204181914.783445-2-maz@kernel.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201204181914.783445-1-maz@kernel.org> References: <20201204181914.783445-1-maz@kernel.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, zhukeqian1@huawei.com, will@kernel.org, wangyanan55@huawei.com, kernel-team@android.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Yanan Wang When installing a new leaf PTE onto an invalid ptep, we need to get_page(ptep) to account for the new mapping. However, simply updating a valid PTE shouldn't result in any additional refcounting, as there is new mapping. This otherwise results in a page being forever wasted. Address this by fixing-up the refcount in stage2_map_walker_try_leaf() if the PTE was already valid, balancing out the later get_page() in stage2_map_walk_leaf(). Signed-off-by: Yanan Wang [maz: update commit message, add comment in the code] Signed-off-by: Marc Zyngier Acked-by: Will Deacon Link: https://lore.kernel.org/r/20201201201034.116760-2-wangyanan55@huawei.com --- arch/arm64/kvm/hyp/pgtable.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 0271b4a3b9fe..2beba1dc40ec 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -470,6 +470,15 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, if (!kvm_block_mapping_supported(addr, end, phys, level)) return false; + /* + * If the PTE was already valid, drop the refcount on the table + * early, as it will be bumped-up again in stage2_map_walk_leaf(). + * This ensures that the refcount stays constant across a valid to + * valid PTE update. + */ + if (kvm_pte_valid(*ptep)) + put_page(virt_to_page(ptep)); + if (kvm_set_valid_leaf_pte(ptep, phys, data->attr, level)) goto out;