When queueing vCPU PVCLOCK updates in response to SUSPEND or HIBERNATE, don't take kvm->lock as doing so can trigger a largely theoretical deadlock, it is perfectly safe to iterate over the xarray of vCPUs without holding kvm->lock, and kvm->lock doesn't protect kvm_set_guest_paused() in any way (pv_time.active and pvclock_set_guest_stopped_request are protected by vcpu->mutex, not kvm->lock). Reported-by: syzbot+352e553a86e0d75f5120@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lore.kernel.org/all/677c0f36.050a0220.3b3668.0014.GAE@xxxxxxxxxx Fixes: 7d62874f69d7 ("kvm: x86: implement KVM PM-notifier") Reviewed-by: Paul Durrant <paul@xxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/x86.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b2d9a16fd4d3..26e18c9b0375 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6907,7 +6907,6 @@ static int kvm_arch_suspend_notifier(struct kvm *kvm) unsigned long i; int ret = 0; - mutex_lock(&kvm->lock); kvm_for_each_vcpu(i, vcpu, kvm) { if (!vcpu->arch.pv_time.active) continue; @@ -6919,7 +6918,6 @@ static int kvm_arch_suspend_notifier(struct kvm *kvm) break; } } - mutex_unlock(&kvm->lock); return ret ? NOTIFY_BAD : NOTIFY_DONE; } -- 2.48.1.362.g079036d154-goog
