linux-kernel - Re: [PATCH] kvm/vfio: Fix potential deadlock problem in vfio

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Date:   Wed, 18 May 2022 11:51:10 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Wan Jiabing <wanjiabing@...o.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Yi Liu <yi.l.liu@...el.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kvm/vfio: Fix potential deadlock problem in vfio

On Tue, 17 May 2022 10:34:41 +0800
Wan Jiabing <wanjiabing@...o.com> wrote:

> Fix following coccicheck warning:
> ./virt/kvm/vfio.c:258:1-7: preceding lock on line 236
> 
> If kvm_vfio_file_iommu_group() failed, code would goto err_fdput with
> mutex_lock acquired and then return ret. It might cause potential
> deadlock. Move mutex_unlock bellow err_fdput tag to fix it. 
> 
> Fixes: d55d9e7a45721 ("kvm/vfio: Store the struct file in the kvm_vfio_group")
> Signed-off-by: Wan Jiabing <wanjiabing@...o.com>
> ---
>  virt/kvm/vfio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index 8f9f7fffb96a..ce1b01d02c51 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -252,8 +252,8 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,
>  		break;
>  	}
>  
> -	mutex_unlock(&kv->lock);
>  err_fdput:
> +	mutex_unlock(&kv->lock);
>  	fdput(f);
>  	return ret;
>  }

Applied to vfio next branch for v5.19.  Thanks!

Alex