From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> BUG: unable to handle kernel NULL pointer dereference at (null) IP: [< (null)>] (null) PGD 0 Oops: 0010 [#1] SMP Call Trace: ? kvm_lapic_expired_hv_timer+0x47/0x90 [kvm] handle_preemption_timer+0xe/0x20 [kvm_intel] vmx_handle_exit+0x169/0x15a0 [kvm_intel] ? kvm_arch_vcpu_ioctl_run+0xd5d/0x19d0 [kvm] kvm_arch_vcpu_ioctl_run+0xdee/0x19d0 [kvm] ? kvm_arch_vcpu_ioctl_run+0xd5d/0x19d0 [kvm] ? vcpu_load+0x1c/0x60 [kvm] ? kvm_arch_vcpu_load+0x57/0x260 [kvm] kvm_vcpu_ioctl+0x2d3/0x7c0 [kvm] do_vfs_ioctl+0x96/0x6a0 ? __fget_light+0x2a/0x90 SyS_ioctl+0x79/0x90 do_syscall_64+0x68/0x180 entry_SYSCALL64_slow_path+0x25/0x25 Code: Bad RIP value. RIP [< (null)>] (null) RSP <ffff8800b5263c48> CR2: 0000000000000000 ---[ end trace 9c70c48b1a2bc66e ]--- This can be reproduced readily by preemption timer enabled on L0 and disabled on L1. Preemption timer for nested VMX is emulated by hrtimer which is started on L2 entry, stopped on L2 exit and evaluated via the check_nested_events hook. However, nested_vmx_exit_handled is always return true for preemption timer vmexit, then the L1 preemption timer vmexit is captured and be treated as a L2 preemption timer vmexit, incurr a nested vmexit dereference NULL pointer. This patch fix it by depending on check_nested_events to capture L2 preemption timer(emulated hrtimer) expire and nested vmexit. Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> Cc: Yunhong Jiang <yunhong.jiang@xxxxxxxxx> Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> Cc: Haozhong Zhang <haozhong.zhang@xxxxxxxxx> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> --- v1 -> v2: * fix typo in patch description arch/x86/kvm/vmx.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 85e2f0a..29c16a8 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8041,6 +8041,8 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu) return nested_cpu_has2(vmcs12, SECONDARY_EXEC_XSAVES); case EXIT_REASON_PCOMMIT: return nested_cpu_has2(vmcs12, SECONDARY_EXEC_PCOMMIT); + case EXIT_REASON_PREEMPTION_TIMER: + return false; default: return true; } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
