Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933240AbdDFI4e (ORCPT ); Thu, 6 Apr 2017 04:56:34 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:53976 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756134AbdDFIqd (ORCPT ); Thu, 6 Apr 2017 04:46:33 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alex Williamson , Jike Song , Paolo Bonzini , Zhenyu Wang , Zhi Wang Subject: [PATCH 4.10 64/81] drm/i915/kvmgt: Hold struct kvm reference Date: Thu, 6 Apr 2017 10:38:56 +0200 Message-Id: <20170406083626.906648260@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170406083624.322941631@linuxfoundation.org> References: <20170406083624.322941631@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1845 Lines: 51 4.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alex Williamson commit 93a15b58cfb8a24e666ffca432f19fe65c1cd7d1 upstream. The kvmgt code keeps a pointer to the struct kvm associated with the device, but doesn't actually hold a reference to it. If we do unclean shutdown testing (ie. killing the user process), then we can see the kvm association to the device unset, which causes kvmgt to trigger a device release via a work queue. Naturally we cannot guarantee that the cached struct kvm pointer is still valid at this point without holding a reference. The observed failure in this case is a stuck cpu trying to acquire the spinlock from the invalid reference, but other failure modes are clearly possible. Hold a reference to avoid this. Signed-off-by: Alex Williamson Cc: Jike Song Cc: Paolo Bonzini Cc: Zhenyu Wang Cc: Zhi Wang Reviewed-by: Jike Song Signed-off-by: Zhenyu Wang Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/gvt/kvmgt.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -1334,6 +1334,7 @@ static int kvmgt_guest_init(struct mdev_ vgpu->handle = (unsigned long)info; info->vgpu = vgpu; info->kvm = kvm; + kvm_get_kvm(info->kvm); kvmgt_protect_table_init(info); gvt_cache_init(vgpu); @@ -1353,6 +1354,7 @@ static bool kvmgt_guest_exit(struct kvmg } kvm_page_track_unregister_notifier(info->kvm, &info->track_node); + kvm_put_kvm(info->kvm); kvmgt_protect_table_destroy(info); gvt_cache_destroy(info->vgpu); vfree(info);