linux-kernel - Re: [PATCH for-4,5] mips/kvm: fix ioctl error handling

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Message-ID: <56D6B3D8.1090000@redhat.com>
Date:	Wed, 2 Mar 2016 10:35:20 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:	stable@...r.kernel.org, James Hogan <james.hogan@...tec.com>,
	Ralf Baechle <ralf@...ux-mips.org>, kvm@...r.kernel.org,
	linux-mips@...ux-mips.org
Subject: Re: [PATCH for-4,5] mips/kvm: fix ioctl error handling



On 28/02/2016 16:35, Michael S. Tsirkin wrote:
> Calling return copy_to_user(...) or return copy_from_user in an ioctl
> will not do the right thing if there's a pagefault:
> copy_to_user/copy_from_user return the number of bytes not copied in
> this case.
> 
> Fix up kvm on mips to do
> 	return copy_to_user(...)) ?  -EFAULT : 0;
> and
> 	return copy_from_user(...)) ?  -EFAULT : 0;
> 
> everywhere.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> 
> Untested.
> 
>  arch/mips/kvm/mips.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 8bc3977..3110447 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -702,7 +702,7 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
>  	} else if ((reg->id & KVM_REG_SIZE_MASK) == KVM_REG_SIZE_U128) {
>  		void __user *uaddr = (void __user *)(long)reg->addr;
>  
> -		return copy_to_user(uaddr, vs, 16);
> +		return copy_to_user(uaddr, vs, 16) ? -EFAULT : 0;
>  	} else {
>  		return -EINVAL;
>  	}
> @@ -732,7 +732,7 @@ static int kvm_mips_set_reg(struct kvm_vcpu *vcpu,
>  	} else if ((reg->id & KVM_REG_SIZE_MASK) == KVM_REG_SIZE_U128) {
>  		void __user *uaddr = (void __user *)(long)reg->addr;
>  
> -		return copy_from_user(vs, uaddr, 16);
> +		return copy_from_user(vs, uaddr, 16) ? -EFAULT : 0;
>  	} else {
>  		return -EINVAL;
>  	}
> 

Applied with the commit message tweak suggested by Sergei.

Paolo