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Subject: Re: [PATCH 2/2] vhost-vdpa: set v->config_ctx to NULL if
 eventfd_ctx_fdget() fails
To:     Stefano Garzarella <sgarzare@redhat.com>,
        virtualization@lists.linux-foundation.org
Cc:     netdev@vger.kernel.org, Zhu Lingshan <lingshan.zhu@intel.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
References: <20210311135257.109460-1-sgarzare@redhat.com>
 <20210311135257.109460-3-sgarzare@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <a5eac458-eed7-df75-66ac-0a8349ad09b0@redhat.com>
Date:   Fri, 12 Mar 2021 14:34:07 +0800
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On 2021/3/11 9:52 下午, Stefano Garzarella wrote:
> In vhost_vdpa_set_config_call() if eventfd_ctx_fdget() fails the
> 'v->config_ctx' contains an error instead of a valid pointer.
>
> Since we consider 'v->config_ctx' valid if it is not NULL, we should
> set it to NULL in this case to avoid to use an invalid pointer in
> other functions such as vhost_vdpa_config_put().
>
> Fixes: 776f395004d8 ("vhost_vdpa: Support config interrupt in vdpa")
> Cc: lingshan.zhu@intel.com
> Cc: stable@vger.kernel.org
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>


Acked-by: Jason Wang <jasowang@redhat.com>


> ---
>   drivers/vhost/vdpa.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 00796e4ecfdf..f9ecdce5468a 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -331,8 +331,12 @@ static long vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp)
>   	if (!IS_ERR_OR_NULL(ctx))
>   		eventfd_ctx_put(ctx);
>   
> -	if (IS_ERR(v->config_ctx))
> -		return PTR_ERR(v->config_ctx);
> +	if (IS_ERR(v->config_ctx)) {
> +		long ret = PTR_ERR(v->config_ctx);
> +
> +		v->config_ctx = NULL;
> +		return ret;
> +	}
>   
>   	v->vdpa->config->set_config_cb(v->vdpa, &cb);
>