Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933091AbcKVTVC (ORCPT ); Tue, 22 Nov 2016 14:21:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42514 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755428AbcKVTVA (ORCPT ); Tue, 22 Nov 2016 14:21:00 -0500 From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , stable@vger.kernel.org, Dmitry Vyukov , Steve Rutherford Subject: [PATCH] KVM: x86: fix out-of-bounds access in lapic Date: Tue, 22 Nov 2016 20:20:14 +0100 Message-Id: <20161122192014.19773-1-rkrcmar@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 22 Nov 2016 19:20:59 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2403 Lines: 57 Cluster xAPIC delivery incorrectly assumed that dest_id <= 0xff. With enabled KVM_X2APIC_API_USE_32BIT_IDS in KVM_CAP_X2APIC_API, a userspace can send an interrupt with dest_id that results in out-of-bounds access. Found by syzkaller: BUG: KASAN: slab-out-of-bounds in kvm_irq_delivery_to_apic_fast+0x11fa/0x1210 at addr ffff88003d9ca750 Read of size 8 by task syz-executor/22923 CPU: 0 PID: 22923 Comm: syz-executor Not tainted 4.9.0-rc4+ #49 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [...] Call Trace: [...] __dump_stack lib/dump_stack.c:15 [...] dump_stack+0xb3/0x118 lib/dump_stack.c:51 [...] kasan_object_err+0x1c/0x70 mm/kasan/report.c:156 [...] print_address_description mm/kasan/report.c:194 [...] kasan_report_error mm/kasan/report.c:283 [...] kasan_report+0x231/0x500 mm/kasan/report.c:303 [...] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:329 [...] kvm_irq_delivery_to_apic_fast+0x11fa/0x1210 arch/x86/kvm/lapic.c:824 [...] kvm_irq_delivery_to_apic+0x132/0x9a0 arch/x86/kvm/irq_comm.c:72 [...] kvm_set_msi+0x111/0x160 arch/x86/kvm/irq_comm.c:157 [...] kvm_send_userspace_msi+0x201/0x280 arch/x86/kvm/../../../virt/kvm/irqchip.c:74 [...] kvm_vm_ioctl+0xba5/0x1670 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3015 [...] vfs_ioctl fs/ioctl.c:43 [...] do_vfs_ioctl+0x18c/0x1040 fs/ioctl.c:679 [...] SYSC_ioctl fs/ioctl.c:694 [...] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [...] entry_SYSCALL_64_fastpath+0x1f/0xc2 Reported-by: Dmitry Vyukov Cc: stable@vger.kernel.org Fixes: e45115b62f9a ("KVM: x86: use physical LAPIC array for logical x2APIC") Signed-off-by: Radim Krčmář --- Cc: Dmitry Vyukov Cc: Steve Rutherford --- arch/x86/kvm/lapic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 09edd32b8e42..34a66b2d47e6 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -138,7 +138,7 @@ static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map, *mask = dest_id & 0xff; return true; case KVM_APIC_MODE_XAPIC_CLUSTER: - *cluster = map->xapic_cluster_map[dest_id >> 4]; + *cluster = map->xapic_cluster_map[(dest_id >> 4) & 0xf]; *mask = dest_id & 0xf; return true; default: -- 2.10.2