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authorWanpeng Li <kernellwp@gmail.com>2018-11-20 09:39:30 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2018-11-27 12:48:56 +0100
commit38ab012f109caf10f471db1adf284e620dd8d701 (patch)
tree202f205bab89f3e44ce3d4c9eab3fae0e5871fec /arch/x86/kvm/lapic.c
parenta87c99e61236ba8ca962ce97a19fab5ebd588d35 (diff)
downloadlinux-38ab012f109caf10f471db1adf284e620dd8d701.tar.bz2
KVM: LAPIC: Fix pv ipis use-before-initialization
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>
Diffstat (limited to 'arch/x86/kvm/lapic.c')
-rw-r--r--arch/x86/kvm/lapic.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 89db20f8cb70..02f2291dcf7e 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -576,6 +576,11 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
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. */