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 6BFBDC433FE for ; Mon, 20 Sep 2021 18:52:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5513660EE4 for ; Mon, 20 Sep 2021 18:52:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386090AbhITSxd (ORCPT ); Mon, 20 Sep 2021 14:53:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:33538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1385515AbhITSue (ORCPT ); Mon, 20 Sep 2021 14:50:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 920C263382; Mon, 20 Sep 2021 17:34:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632159294; bh=GDh1oJgfaumRs5nc3q4ACijDRerreORaEJwNHlV1E4I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fI5kZwtOIH//2LeVMlcXQguAE4k13o4c3IBoUD+bSRxf78bSzC44nGfNoWdqxyqb3 0sCU+3YYp64mgUzCJXwugCNx+o7XvSgbS01C0EsIEms88reETqMuYEshRbCa1KGR8g nKumZ9GTmvVu6ptVdF1sfETUaogvLkP48HJsP8qU= 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 5.14 133/168] KVM: arm64: Fix read-side race on updates to vcpu reset state Date: Mon, 20 Sep 2021 18:44:31 +0200 Message-Id: <20210920163926.039345484@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163921.633181900@linuxfoundation.org> References: <20210920163921.633181900@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 78d4bd897fbc..d010778b93ff 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -210,10 +210,16 @@ 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); @@ -276,8 +282,8 @@ 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)) { @@ -286,13 +292,11 @@ 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