From mboxrd@z Thu Jan 1 00:00:00 1970 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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 44331C433FE for ; Mon, 20 Sep 2021 18:35:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3059E60F6D for ; Mon, 20 Sep 2021 18:35:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353100AbhITShH (ORCPT ); Mon, 20 Sep 2021 14:37:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:49242 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380082AbhITSc1 (ORCPT ); Mon, 20 Sep 2021 14:32:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0874961425; Mon, 20 Sep 2021 17:27:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632158869; bh=68THdfiFeOKS8g83uwolAWRGbPZ1OGzwp8L7fbCTySo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CCYbdHKKzOCrYmVx+on0uKTpgVOoVGQZQL7IpOij9BKuhRHMlwQlvgquAKh7rt4XW u9e+eEuIwMeEaon+GK1q3ra5KEjrGn2wny8hWeDNzD7fiPSes8XXCTVkPBUgD4I6sh jiWYYbAMtX9BOB9swwghVhAm+6xt8b6J471V0CTg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oliver Upton , Marc Zyngier , Sasha Levin Subject: [PATCH 5.10 092/122] KVM: arm64: Fix read-side race on updates to vcpu reset state Date: Mon, 20 Sep 2021 18:44:24 +0200 Message-Id: <20210920163918.802009584@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163915.757887582@linuxfoundation.org> References: <20210920163915.757887582@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oliver Upton [ Upstream commit 6654f9dfcb88fea3b9affc180dc3c04333d0f306 ] KVM correctly serializes writes to a vCPU's reset state, however since we do not take the KVM lock on the read side it is entirely possible to read state from two different reset requests. Cure the race for now by taking the KVM lock when reading the reset_state structure. Fixes: 358b28f09f0a ("arm/arm64: KVM: Allow a VCPU to fully reset itself") Signed-off-by: Oliver Upton Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210818202133.1106786-2-oupton@google.com Signed-off-by: Sasha Levin --- arch/arm64/kvm/reset.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index 6058a80ec9ec..204c62debf06 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -263,10 +263,16 @@ static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu) */ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) { + struct vcpu_reset_state reset_state; int ret; bool loaded; u32 pstate; + mutex_lock(&vcpu->kvm->lock); + reset_state = vcpu->arch.reset_state; + WRITE_ONCE(vcpu->arch.reset_state.reset, false); + mutex_unlock(&vcpu->kvm->lock); + /* Reset PMU outside of the non-preemptible section */ kvm_pmu_vcpu_reset(vcpu); @@ -325,8 +331,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) * Additional reset state handling that PSCI may have imposed on us. * Must be done after all the sys_reg reset. */ - if (vcpu->arch.reset_state.reset) { - unsigned long target_pc = vcpu->arch.reset_state.pc; + if (reset_state.reset) { + unsigned long target_pc = reset_state.pc; /* Gracefully handle Thumb2 entry point */ if (vcpu_mode_is_32bit(vcpu) && (target_pc & 1)) { @@ -335,13 +341,11 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) } /* Propagate caller endianness */ - if (vcpu->arch.reset_state.be) + if (reset_state.be) kvm_vcpu_set_be(vcpu); *vcpu_pc(vcpu) = target_pc; - vcpu_set_reg(vcpu, 0, vcpu->arch.reset_state.r0); - - vcpu->arch.reset_state.reset = false; + vcpu_set_reg(vcpu, 0, reset_state.r0); } /* Reset timer */ -- 2.30.2