linux-kernel - Re: [PATCH] block: xen-blkback: add null check to avoid null pointer dereference

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Date:   Mon, 15 May 2017 17:18:44 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Roger Pau Monné <roger.pau@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: xen-blkback: add null check to avoid null pointer
 dereference

On Thu, May 11, 2017 at 10:27:35AM -0500, Gustavo A. R. Silva wrote:
> Add null check before calling xen_blkif_put() to avoid potential
> null pointer dereference.
> 

Applied to 'stable/for-jens-4.12' and will push soon to Jens.

> Addresses-Coverity-ID: 1350942
> Cc: Juergen Gross <jgross@...e.com>
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> ---
>  drivers/block/xen-blkback/xenbus.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index 8fe61b5..1f3dfaa 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -504,11 +504,13 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
>  
>  	dev_set_drvdata(&dev->dev, NULL);
>  
> -	if (be->blkif)
> +	if (be->blkif) {
>  		xen_blkif_disconnect(be->blkif);
>  
> -	/* Put the reference we set in xen_blkif_alloc(). */
> -	xen_blkif_put(be->blkif);
> +		/* Put the reference we set in xen_blkif_alloc(). */
> +		xen_blkif_put(be->blkif);
> +	}
> +
>  	kfree(be->mode);
>  	kfree(be);
>  	return 0;
> -- 
> 2.5.0
>