6.1-stable review patch. If anyone has any objections, please let me know.
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From: Marc Zyngier maz@kernel.org
commit df5fd75ee305cb5927e0b1a0b46cc988ad8db2b1 upstream.
As there is very little ordering in the KVM API, userspace can instanciate a half-baked GIC (missing its memory map, for example) at almost any time.
This means that, with the right timing, a thread running vcpu-0 can enter the kernel without a GIC configured and get a GIC created behind its back by another thread. Amusingly, it will pick up that GIC and start messing with the data structures without the GIC having been fully initialised.
Similarly, a thread running vcpu-1 can enter the kernel, and try to init the GIC that was previously created. Since this GIC isn't properly configured (no memory map), it fails to correctly initialise.
And that's the point where we decide to teardown the GIC, freeing all its resources. Behind vcpu-0's back. Things stop pretty abruptly, with a variety of symptoms. Clearly, this isn't good, we should be a bit more careful about this.
It is obvious that this guest is not viable, as it is missing some important part of its configuration. So instead of trying to tear bits of it down, let's just mark it as *dead*. It means that any further interaction from userspace will result in -EIO. The memory will be released on the "normal" path, when userspace gives up.
Cc: stable@vger.kernel.org Reported-by: Alexander Potapenko glider@google.com Reviewed-by: Oliver Upton oliver.upton@linux.dev Link: https://lore.kernel.org/r/20241009183603.3221824-1-maz@kernel.org Signed-off-by: Marc Zyngier maz@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kvm/arm.c | 3 +++ arch/arm64/kvm/vgic/vgic-init.c | 6 +++--- 2 files changed, 6 insertions(+), 3 deletions(-)
--- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -750,6 +750,9 @@ static int kvm_vcpu_suspend(struct kvm_v static int check_vcpu_requests(struct kvm_vcpu *vcpu) { if (kvm_request_pending(vcpu)) { + if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) + return -EIO; + if (kvm_check_request(KVM_REQ_SLEEP, vcpu)) kvm_vcpu_sleep(vcpu);
--- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -494,10 +494,10 @@ int kvm_vgic_map_resources(struct kvm *k out: mutex_unlock(&kvm->arch.config_lock); out_slots: - mutex_unlock(&kvm->slots_lock); - if (ret) - kvm_vgic_destroy(kvm); + kvm_vm_dead(kvm); + + mutex_unlock(&kvm->slots_lock);
return ret; }