Re: [PATCH v4 3/3] LoongArch: KVM: Reject repeated PCH-PIC CTRL_INIT

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] kvm: loongarch: missing rollback of s->device.ops on IO bus registration failure
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commit d13a3fd9c70a7a0b0118a0e9dbae30ac5e61efaa
Author: Tao Cui <cuitao@kylinos.cn>

LoongArch: KVM: Reject repeated PCH-PIC CTRL_INIT

This commit adds a check to prevent repeated PCH-PIC initialization. It
rejects multiple ioctl calls with -EEXIST by verifying if the device
ops are already populated.

> diff --git a/arch/loongarch/kvm/intc/pch_pic.c b/arch/loongarch/kvm/intc/pch_pic.c
> index 51e4a6a39dc06..a4c35ed704be8 100644
> --- a/arch/loongarch/kvm/intc/pch_pic.c
> +++ b/arch/loongarch/kvm/intc/pch_pic.c
> @@ -281,16 +281,21 @@ static int kvm_pch_pic_init(struct kvm_device *dev, u64 addr)
>  	struct kvm_io_device *device;
>  	struct loongarch_pch_pic *s = dev->kvm->arch.pch_pic;
>  
> -	s->pch_pic_base = addr;
>  	device = &s->device;
> +	mutex_lock(&kvm->slots_lock);
> +	if (s->device.ops) {
> +		ret = -EEXIST;
> +		goto out;
> +	}
> +	s->pch_pic_base = addr;
>  	/* init device by pch pic writing and reading ops */
>  	kvm_iodevice_init(device, &kvm_pch_pic_ops);
> -	mutex_lock(&kvm->slots_lock);
>  	/* register pch pic device */
>  	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, addr, PCH_PIC_SIZE, device);
> +out:
>  	mutex_unlock(&kvm->slots_lock);
>  
> -	return (ret < 0) ? -EFAULT : 0;
> +	return ret;

[Severity: Low]
Does this error path leave the device partially initialized if
kvm_io_bus_register_dev() fails?

If kvm_io_bus_register_dev() returns an error (e.g. -ENOMEM), ret is set
to the error code, but s->device.ops has already been populated by
kvm_iodevice_init() earlier in kvm_pch_pic_init().

Since the function now uses s->device.ops to check for initialization,
would this prevent userspace from retrying the initialization? Subsequent
calls will see s->device.ops populated and return -EEXIST.

>  }
>  
>  /* used by user space to get or set pch pic registers */

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Sashiko AI review · https://sashiko.dev/#/patchset/20261015234638.1077815-1-cui.tao@linux.dev?part=3