@@ -7012,20 +7012,24 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
unsigned int id)
{
struct kvm_vcpu *vcpu;
if (check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
printk_once(KERN_WARNING
"kvm: SMP vm created on host with unstable TSC; "
"guest TSC will not be reliable\n");
vcpu = kvm_x86_ops->vcpu_create(kvm, id);
+ if (IS_ERR(vcpu)) {
+ pr_err("kvm_x86_ops->vcpu_create id=%u err=%ld\n", id,
PTR_ERR(vcpu));
+ return vcpu;
+ }
/*
* Activate fpu unconditionally in case the guest needs eager FPU. It
will be
* deactivated soon if it doesn't.
*/
kvm_x86_ops->fpu_activate(vcpu);
return vcpu;
}
https://bugzilla.kernel.org/show_bug.cgi?id=103141 Alex Lyakas (alex@zadara.com) changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |alex@zadara.com --- Comment #4 from Alex Lyakas (alex@zadara.com) --- We hit the same issue with kernel 3.18.19. After some debugging, I see that the first test program that felix attached, causes kvm_x86_ops->vcpu_create to return -EEXIST instead of a valid vcpu pointer. As a result, the call to kvm_x86_ops->fpu_activate tries to access an invalid pointer, and causes a NULL pointer dereference. The suggested fix was delivered in kernel 4.2. Although it was tagged as "stable", I don't see that it was backported to earlier kernels. I believe that the fix addresses a different issue, in which the vcpu pointer is valid, but further VMCS write has a problem (this is my understanding). But, of course, this fix will address also the issue that felix reported. Although for the latter, a simpler fix would suffice: