From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754940AbdAADpB (ORCPT ); Sat, 31 Dec 2016 22:45:01 -0500 Received: from mail-pg0-f67.google.com ([74.125.83.67]:34585 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754625AbdAADpA (ORCPT ); Sat, 31 Dec 2016 22:45:00 -0500 From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Dmitry Vyukov , Wanpeng Li Subject: [PATCH] KVM: ioapic: fix NULL deref ioapic->lock Date: Sat, 31 Dec 2016 19:44:49 -0800 Message-Id: <1483242289-12323-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li This was reported by syzkaller: BUG: unable to handle kernel NULL pointer dereference at 00000000000001b0 IP: _raw_spin_lock+0xc/0x30 PGD 3e28eb067 PUD 3f0ac6067 PMD 0 Oops: 0002 [#1] SMP CPU: 0 PID: 2431 Comm: test Tainted: G OE 4.10.0-rc1+ #3 Call Trace: ? kvm_ioapic_scan_entry+0x3e/0x110 [kvm] kvm_arch_vcpu_ioctl_run+0x10a8/0x15f0 [kvm] ? pick_next_task_fair+0xe1/0x4e0 ? kvm_arch_vcpu_load+0xea/0x260 [kvm] kvm_vcpu_ioctl+0x33a/0x600 [kvm] ? hrtimer_try_to_cancel+0x29/0x130 ? do_nanosleep+0x97/0xf0 do_vfs_ioctl+0xa1/0x5d0 ? __hrtimer_init+0x90/0x90 ? do_nanosleep+0x5b/0xf0 SyS_ioctl+0x79/0x90 do_syscall_64+0x6e/0x180 entry_SYSCALL64_slow_path+0x25/0x25 RIP: _raw_spin_lock+0xc/0x30 RSP: ffffa43688973cc0 KVM will skip over create pic/ioapic if there is a created vCPU. However, there is no guarantee whether ioapic is present when rescan ioapic which results in NULL dereference ioapic->lock. This patch fix it by adding the ioapic present check to ioapic scan. Reported-by: Dmitry Vyukov Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li --- arch/x86/kvm/x86.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 51ccfe0..9ca175c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6556,7 +6556,8 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu) else { if (vcpu->arch.apicv_active) kvm_x86_ops->sync_pir_to_irr(vcpu); - kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors); + if (ioapic_irqchip(vcpu->kvm)) + kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors); } bitmap_or((ulong *)eoi_exit_bitmap, vcpu->arch.ioapic_handled_vectors, vcpu_to_synic(vcpu)->vec_bitmap, 256); -- 2.7.4