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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2CF3C433F5 for ; Mon, 1 Nov 2021 09:50:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B99ED60C41 for ; Mon, 1 Nov 2021 09:50:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232348AbhKAJww (ORCPT ); Mon, 1 Nov 2021 05:52:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:54296 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234431AbhKAJut (ORCPT ); Mon, 1 Nov 2021 05:50:49 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 79E9361506; Mon, 1 Nov 2021 09:32:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1635759124; bh=DLU0hoLPn9aOJSaWhDSMMKarff5wLgOVFaMK8lio7N8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NTKqX+Ek1SCkDwKUlknBZvpIIGpZeCzq+/uuLCXgRqnjR7pRNqAVwuD9OqZRuIPFV jH8vlUL8rQVgM+ivI+Bc6XSNuNtvva6s7H/Aujd/X211biF8aUGF1f2kcMV3hosbnZ a2xiol/3yqeRx/H/1qbKnvvahw8zyiWvJGEi8KRE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Woodhouse , Paolo Bonzini Subject: [PATCH 5.14 125/125] KVM: x86: Take srcu lock in post_kvm_run_save() Date: Mon, 1 Nov 2021 10:18:18 +0100 Message-Id: <20211101082556.682702250@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211101082533.618411490@linuxfoundation.org> References: <20211101082533.618411490@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: stable@vger.kernel.org From: David Woodhouse commit f3d1436d4bf8ced1c9a62a045d193a65567e1fcc upstream. The Xen interrupt injection for event channels relies on accessing the guest's vcpu_info structure in __kvm_xen_has_interrupt(), through a gfn_to_hva_cache. This requires the srcu lock to be held, which is mostly the case except for this code path: [ 11.822877] WARNING: suspicious RCU usage [ 11.822965] ----------------------------- [ 11.823013] include/linux/kvm_host.h:664 suspicious rcu_dereference_check() usage! [ 11.823131] [ 11.823131] other info that might help us debug this: [ 11.823131] [ 11.823196] [ 11.823196] rcu_scheduler_active = 2, debug_locks = 1 [ 11.823253] 1 lock held by dom:0/90: [ 11.823292] #0: ffff998956ec8118 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0x85/0x680 [ 11.823379] [ 11.823379] stack backtrace: [ 11.823428] CPU: 2 PID: 90 Comm: dom:0 Kdump: loaded Not tainted 5.4.34+ #5 [ 11.823496] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 [ 11.823612] Call Trace: [ 11.823645] dump_stack+0x7a/0xa5 [ 11.823681] lockdep_rcu_suspicious+0xc5/0x100 [ 11.823726] __kvm_xen_has_interrupt+0x179/0x190 [ 11.823773] kvm_cpu_has_extint+0x6d/0x90 [ 11.823813] kvm_cpu_accept_dm_intr+0xd/0x40 [ 11.823853] kvm_vcpu_ready_for_interrupt_injection+0x20/0x30 < post_kvm_run_save() inlined here > [ 11.823906] kvm_arch_vcpu_ioctl_run+0x135/0x6a0 [ 11.823947] kvm_vcpu_ioctl+0x263/0x680 Fixes: 40da8ccd724f ("KVM: x86/xen: Add event channel interrupt vector upcall") Signed-off-by: David Woodhouse Cc: stable@vger.kernel.org Message-Id: <606aaaf29fca3850a63aa4499826104e77a72346.camel@infradead.org> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8799,9 +8799,17 @@ static void post_kvm_run_save(struct kvm kvm_run->cr8 = kvm_get_cr8(vcpu); kvm_run->apic_base = kvm_get_apic_base(vcpu); + + /* + * The call to kvm_ready_for_interrupt_injection() may end up in + * kvm_xen_has_interrupt() which may require the srcu lock to be + * held, to protect against changes in the vcpu_info address. + */ + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); kvm_run->ready_for_interrupt_injection = pic_in_kernel(vcpu->kvm) || kvm_vcpu_ready_for_interrupt_injection(vcpu); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); if (is_smm(vcpu)) kvm_run->flags |= KVM_RUN_X86_SMM;