| From 38ab012f109caf10f471db1adf284e620dd8d701 Mon Sep 17 00:00:00 2001 |
| From: Wanpeng Li <kernellwp@gmail.com> |
| Date: Tue, 20 Nov 2018 09:39:30 +0800 |
| Subject: KVM: LAPIC: Fix pv ipis use-before-initialization |
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| Content-Type: text/plain; charset=UTF-8 |
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| |
| From: Wanpeng Li <kernellwp@gmail.com> |
| |
| commit 38ab012f109caf10f471db1adf284e620dd8d701 upstream. |
| |
| Reported by syzkaller: |
| |
| BUG: unable to handle kernel NULL pointer dereference at 0000000000000014 |
| PGD 800000040410c067 P4D 800000040410c067 PUD 40410d067 PMD 0 |
| Oops: 0000 [#1] PREEMPT SMP PTI |
| CPU: 3 PID: 2567 Comm: poc Tainted: G OE 4.19.0-rc5 #16 |
| RIP: 0010:kvm_pv_send_ipi+0x94/0x350 [kvm] |
| Call Trace: |
| kvm_emulate_hypercall+0x3cc/0x700 [kvm] |
| handle_vmcall+0xe/0x10 [kvm_intel] |
| vmx_handle_exit+0xc1/0x11b0 [kvm_intel] |
| vcpu_enter_guest+0x9fb/0x1910 [kvm] |
| kvm_arch_vcpu_ioctl_run+0x35c/0x610 [kvm] |
| kvm_vcpu_ioctl+0x3e9/0x6d0 [kvm] |
| do_vfs_ioctl+0xa5/0x690 |
| ksys_ioctl+0x6d/0x80 |
| __x64_sys_ioctl+0x1a/0x20 |
| do_syscall_64+0x83/0x6e0 |
| entry_SYSCALL_64_after_hwframe+0x49/0xbe |
| |
| The reason is that the apic map has not yet been initialized, the testcase |
| triggers pv_send_ipi interface by vmcall which results in kvm->arch.apic_map |
| is dereferenced. This patch fixes it by checking whether or not apic map is |
| NULL and bailing out immediately if that is the case. |
| |
| Fixes: 4180bf1b65 (KVM: X86: Implement "send IPI" hypercall) |
| Reported-by: Wei Wu <ww9210@gmail.com> |
| Cc: Paolo Bonzini <pbonzini@redhat.com> |
| Cc: Radim Krčmář <rkrcmar@redhat.com> |
| Cc: Wei Wu <ww9210@gmail.com> |
| Signed-off-by: Wanpeng Li <wanpengli@tencent.com> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/x86/kvm/lapic.c | 5 +++++ |
| 1 file changed, 5 insertions(+) |
| |
| --- a/arch/x86/kvm/lapic.c |
| +++ b/arch/x86/kvm/lapic.c |
| @@ -571,6 +571,11 @@ int kvm_pv_send_ipi(struct kvm *kvm, uns |
| rcu_read_lock(); |
| map = rcu_dereference(kvm->arch.apic_map); |
| |
| + if (unlikely(!map)) { |
| + count = -EOPNOTSUPP; |
| + goto out; |
| + } |
| + |
| if (min > map->max_apic_id) |
| goto out; |
| /* Bits above cluster_size are masked in the caller. */ |
