linux-kernel - Re: [PATCH 01/11] KVM: PPC: Book3S HV: Move assignments for the variable "err" in kvm_htab

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Message-ID: <7e09721f-2785-4c34-cfe8-593acafc455e@redhat.com>
Date:   Mon, 23 Jan 2017 15:12:55 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     SF Markus Elfring <elfring@...rs.sourceforge.net>,
        kvm@...r.kernel.org, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, Alexander Graf <agraf@...e.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 01/11] KVM: PPC: Book3S HV: Move assignments for the
 variable "err" in kvm_htab_write()



On 20/01/2017 19:19, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Thu, 19 Jan 2017 22:45:56 +0100
> 
> * A local variable was set to an error code in five cases
>   before a concrete error situation was detected.
>   Thus move the corresponding assignments into
>   if branches to indicate a software failure there.
> 
>   This issue was detected by using the Coccinelle software.
> 
> * Delete two zero assignments which became unnecessary with
>   this refactoring.
> 
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>

NACK, current code uses consistent style.

> ---
>  arch/powerpc/kvm/book3s_64_mmu_hv.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index b795dd1ac2ef..dc34729e4ad0 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -1399,22 +1399,23 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
>  
>  	err = 0;
>  	for (nb = 0; nb + sizeof(hdr) <= count; ) {
> -		err = -EFAULT;
> -		if (__copy_from_user(&hdr, buf, sizeof(hdr)))
> +		if (__copy_from_user(&hdr, buf, sizeof(hdr))) {
> +			err = -EFAULT;
>  			break;
> +		}
>  
> -		err = 0;
>  		if (nb + hdr.n_valid * HPTE_SIZE > count)
>  			break;
>  
>  		nb += sizeof(hdr);
>  		buf += sizeof(hdr);
>  
> -		err = -EINVAL;
>  		i = hdr.index;
>  		if (i >= kvm->arch.hpt_npte ||
> -		    i + hdr.n_valid + hdr.n_invalid > kvm->arch.hpt_npte)
> +		    i + hdr.n_valid + hdr.n_invalid > kvm->arch.hpt_npte) {
> +			err = -EINVAL;
>  			break;
> +		}
>  
>  		hptp = (__be64 *)(kvm->arch.hpt_virt + (i * HPTE_SIZE));
>  		lbuf = (unsigned long __user *)buf;
> @@ -1422,26 +1423,28 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
>  			__be64 hpte_v;
>  			__be64 hpte_r;
>  
> -			err = -EFAULT;
>  			if (__get_user(hpte_v, lbuf) ||
> -			    __get_user(hpte_r, lbuf + 1))
> +			    __get_user(hpte_r, lbuf + 1)) {
> +				err = -EFAULT;
>  				goto out;
> +			}
>  			v = be64_to_cpu(hpte_v);
>  			r = be64_to_cpu(hpte_r);
> -			err = -EINVAL;
> -			if (!(v & HPTE_V_VALID))
> +			if (!(v & HPTE_V_VALID)) {
> +				err = -EINVAL;
>  				goto out;
> +			}
>  			lbuf += 2;
>  			nb += HPTE_SIZE;
>  
>  			if (be64_to_cpu(hptp[0]) & (HPTE_V_VALID | HPTE_V_ABSENT))
>  				kvmppc_do_h_remove(kvm, 0, i, 0, tmp);
> -			err = -EIO;
>  			ret = kvmppc_virtmode_do_h_enter(kvm, H_EXACT, i, v, r,
>  							 tmp);
>  			if (ret != H_SUCCESS) {
>  				pr_err("kvm_htab_write ret %ld i=%ld v=%lx "
>  				       "r=%lx\n", ret, i, v, r);
> +				err = -EIO;
>  				goto out;
>  			}
>  			if (!hpte_setup && is_vrma_hpte(v)) {
> @@ -1465,7 +1468,6 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
>  			++i;
>  			hptp += 2;
>  		}
> -		err = 0;
>  	}
>  
>   out:
>