From 4d6092feade85f09e689386595757ee1d4422707 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Mon, 17 Dec 2018 10:43:23 +0800 Subject: [PATCH] KVM: X86: Fix NULL deref in vcpu_scan_ioapic MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit dcbd3e49c2f0b2c2d8a321507ff8f3de4af76d7c upstream. Reported by syzkaller: CPU: 1 PID: 5962 Comm: syz-executor118 Not tainted 4.20.0-rc6+ #374 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:kvm_apic_hw_enabled arch/x86/kvm/lapic.h:169 [inline] RIP: 0010:vcpu_scan_ioapic arch/x86/kvm/x86.c:7449 [inline] RIP: 0010:vcpu_enter_guest arch/x86/kvm/x86.c:7602 [inline] RIP: 0010:vcpu_run arch/x86/kvm/x86.c:7874 [inline] RIP: 0010:kvm_arch_vcpu_ioctl_run+0x5296/0x7320 arch/x86/kvm/x86.c:8074 Call Trace: kvm_vcpu_ioctl+0x5c8/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2596 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe The reason is that the testcase writes hyperv synic HV_X64_MSR_SINT14 msr and triggers scan ioapic logic to load synic vectors into EOI exit bitmap. However, irqchip is not initialized by this simple testcase, ioapic/apic objects should not be accessed. This patch fixes it by also considering whether or not apic is present. Reported-by: syzbot+39810e6c400efadfef71@syzkaller.appspotmail.com Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- arch/x86/kvm/x86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 951735eea29aaf..e78cb7aa196aae 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6054,7 +6054,7 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu) u64 eoi_exit_bitmap[4]; u32 tmr[8]; - if (!kvm_apic_hw_enabled(vcpu->arch.apic)) + if (!kvm_apic_present(vcpu)) return; memset(eoi_exit_bitmap, 0, 32);