linux-kernel - Re: [PATCH] KVM: x86: Use ERR_PTR_USR() to return -EFAULT as a _

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Message-ID: <3874109c-d086-f657-6452-0cab7fc0c29e@redhat.com>
Date:   Fri, 4 Feb 2022 09:44:38 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Use ERR_PTR_USR() to return -EFAULT as a __user
 pointer

On 2/2/22 01:51, Sean Christopherson wrote:
> Use ERR_PTR_USR() when returning -EFAULT from kvm_get_attr_addr(), sparse
> complains about implicitly casting the kernel pointer from ERR_PTR() into
> a __user pointer.
> 
>>> arch/x86/kvm/x86.c:4342:31: sparse: sparse: incorrect type in return expression
>     (different address spaces) @@     expected void [noderef] __user * @@     got void * @@
>     arch/x86/kvm/x86.c:4342:31: sparse:     expected void [noderef] __user *
>     arch/x86/kvm/x86.c:4342:31: sparse:     got void *
>>> arch/x86/kvm/x86.c:4342:31: sparse: sparse: incorrect type in return expression
>     (different address spaces) @@     expected void [noderef] __user * @@     got void * @@
>     arch/x86/kvm/x86.c:4342:31: sparse:     expected void [noderef] __user *
>     arch/x86/kvm/x86.c:4342:31: sparse:     got void *
> 
> No functional change intended.
> 
> Fixes: 56f289a8d23a ("KVM: x86: Add a helper to retrieve userspace address from kvm_device_attr")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/x86/kvm/x86.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fec3dd4f0718..b533aab98172 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -90,6 +90,8 @@
>   u64 __read_mostly kvm_mce_cap_supported = MCG_CTL_P | MCG_SER_P;
>   EXPORT_SYMBOL_GPL(kvm_mce_cap_supported);
>   
> +#define  ERR_PTR_USR(e)  ((void __user *)ERR_PTR(e))
> +
>   #define emul_to_vcpu(ctxt) \
>   	((struct kvm_vcpu *)(ctxt)->vcpu)
>   
> @@ -4340,7 +4342,7 @@ static inline void __user *kvm_get_attr_addr(struct kvm_device_attr *attr)
>   	void __user *uaddr = (void __user*)(unsigned long)attr->addr;
>   
>   	if ((u64)(unsigned long)uaddr != attr->addr)
> -		return ERR_PTR(-EFAULT);
> +		return ERR_PTR_USR(-EFAULT);
>   	return uaddr;
>   }
>   
> @@ -11684,8 +11686,6 @@ void kvm_arch_sync_events(struct kvm *kvm)
>   	kvm_free_pit(kvm);
>   }
>   
> -#define  ERR_PTR_USR(e)  ((void __user *)ERR_PTR(e))
> -
>   /**
>    * __x86_set_memory_region: Setup KVM internal memory slot
>    *
> 
> base-commit: b2d2af7e5df37ee3a9ba6b405bdbb7691a5c2dfc

Queued, thanks.

Paolo