Re: [PATCH v2 4/7] KVM: Protect all of kvm_vm_ioctl_create_vcpu() with kvm->lock

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] kvm: mixing goto-based error handling with guard() in kvm_vm_ioctl_create_vcpu
--

commit 01402bb146d901e6f480f96bad9c9a7b5314ecb9
Author: Sean Christopherson <seanjc@google.com>

KVM: Protect all of kvm_vm_ioctl_create_vcpu() with kvm->lock

This commit serializes vCPU creation by holding the kvm->lock for the
entirety of kvm_vm_ioctl_create_vcpu(). It removes the manual lock/unlock calls
that previously existed around parts of the creation process and replaces them
with a scoped guard.

> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4165,6 +4165,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id)
>  	struct kvm_vcpu *vcpu;
>  	struct page *page;
>  
> +	guard(mutex)(&kvm->lock);
> +
>  	/*
>  	 * KVM tracks vCPU IDs as 'int', be kind to userspace and reject

[ ... ]

> @@ -4287,10 +4277,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id)
>  vcpu_free:
>  	kmem_cache_free(kvm_vcpu_cache, vcpu);
>  vcpu_decrement:
> -	mutex_lock(&kvm->lock);
>  	kvm->created_vcpus--;
>  	__clear_bit(id, kvm->vcpu_ids);
> -	mutex_unlock(&kvm->lock);
>  	return r;
>  }

[Severity: Low]
Does kvm_vm_ioctl_create_vcpu() in virt/kvm/kvm_main.c mix goto-based error
handling with the new scope-based guard()?

The cleanup subsystem guidelines forbid mixing scope-based guard() with
legacy goto error handling in the same function, as it creates confusing
ownership semantics and risks future double-free or resource leak bugs
during maintenance.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260921174445.911676-1-seanjc@google.com?part=4