The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From a1fa4cbd53d9bc7bb0eaa7bcf7c8a5904372a4ec Mon Sep 17 00:00:00 2001 From: Wanpeng Li <wanpengli@xxxxxxxxxxx> Date: Fri, 9 Apr 2021 12:18:31 +0800 Subject: [PATCH] KVM: X86: Do not yield to self If the target is self we do not need to yield, we can avoid malicious guest to play this. Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx> Message-Id: <1617941911-5338-3-git-send-email-wanpengli@xxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 05a4bce181d7..66d2ab074a5f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8228,6 +8228,10 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id) if (!target || !READ_ONCE(target->ready)) goto no_yield; + /* Ignore requests to yield to self */ + if (vcpu == target) + goto no_yield; + if (kvm_vcpu_yield_to(target) <= 0) goto no_yield;
