linux-kernel - Re: [Xen-devel] [PATCH] pvcalls-front: fixes incorrect error handling

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Date:   Mon, 26 Nov 2018 15:31:39 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Pan Bian <bianpan2016@....com>, Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] pvcalls-front: fixes incorrect error handling

On 11/21/18 9:07 PM, Pan Bian wrote:
> kfree() is incorrectly used to release the pages allocated by
> __get_free_page() and __get_free_pages(). Use the matching deallocators
> i.e., free_page() and free_pages(), respectively.
>
> Signed-off-by: Pan Bian <bianpan2016@....com>
> ---
>  drivers/xen/pvcalls-front.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> index 2f11ca7..77224d8 100644
> --- a/drivers/xen/pvcalls-front.c
> +++ b/drivers/xen/pvcalls-front.c
> @@ -385,8 +385,8 @@ static int create_active(struct sock_mapping *map, int *evtchn)
>  out_error:
>  	if (*evtchn >= 0)
>  		xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
> -	kfree(map->active.data.in);
> -	kfree(map->active.ring);
> +	free_pages((unsigned long)map->active.data.in, PVCALLS_RING_ORDER);

Is map->active.data.in guaranteed to be NULL when entering this routine?

-boris

> +	free_page((unsigned long)map->active.ring);
>  	return ret;
>  }
>