linux-kernel - Re: [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

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Message-ID: <20080512193754.70c65c5d@vitb-lp>
Date:	Mon, 12 May 2008 19:37:54 +0400
From:	Vitaly Bordug <vbordug@...mvista.com>
To:	Julia Lawall <julia@...u.dk>
Cc:	pantelis.antoniou@...il.com, linuxppc-dev@...abs.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 4/6] drivers/net/fs_enet: remove null pointer
 dereference

On Mon, 12 May 2008 15:38:26 +0200 (CEST)
Julia Lawall wrote:

> From: Julia Lawall <julia@...u.dk>
Acked-by: Vitaly Bordug <vitb@...nel.crashing.org>

> 
> The following code appears in the function fs_init_instance in the
> file drivers/net/fs_enet/fs_enet-main.c.
> 
> 	if (fep->ops == NULL) {
> 		printk(KERN_ERR DRV_MODULE_NAME
> 		       ": %s No matching ops found (%d).\n",
> 		       ndev->name, fpi->fs_no);
> 		err = -EINVAL;
> 		goto err;
> 	}
> 
> This code implies that at the point of err, fep->ops can be NULL, so
> an extra test is needed before dereferencing this value.
> 

> 
> This problem was found using the following semantic match
> (http://www.emn.fr/x-info/coccinelle/)
> 
> // <smpl>
> @@
> expression E, E1;
> identifier f;
> statement S1,S2,S3;
> @@
> 
> * if (E == NULL)
> {
>   ... when != if (E == NULL) S1 else S2
>       when != E = E1
> * E->f
>   ... when any
>   return ...;
> }
> else S3
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>
> 
> ---
> 
> diff -u -p a/drivers/net/fs_enet/fs_enet-main.c
> b/drivers/net/fs_enet/fs_enet-main.c ---
> a/drivers/net/fs_enet/fs_enet-main.c	2008-04-27
> 11:41:11.000000000 +0200 +++
> b/drivers/net/fs_enet/fs_enet-main.c	2008-05-12
> 09:41:52.000000000 +0200 @@ -1093,7 +1093,7 @@ err: if (registered)
> unregister_netdev(ndev); 
> -		if (fep != NULL) {
> +		if (fep && fep->ops) {
>  			(*fep->ops->free_bd)(ndev);
>  			(*fep->ops->cleanup_data)(ndev);
>  		}

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