netdev - Re: nfc: nci: fix potential NULL pointer dereference

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Date:   Mon, 12 Jun 2017 15:21:55 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Samuel Ortiz <sameo@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: nfc: nci: fix potential NULL pointer dereference

On Mon, Jun 12, 2017 at 05:02:23PM -0500, Gustavo A. R. Silva wrote:
> NULL check at line 76: if (conn_info) {, implies that pointer conn_info
> might be NULL, but this pointer is being previously dereferenced,
> which might cause a NULL pointer dereference.
> 
> Add NULL check before dereferencing pointer conn_info in order to
> avoid a potential NULL pointer dereference.
> 
> Addresses-Coverity-ID: 1362349
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> ---
>  net/nfc/nci/core.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
> index 61fff42..d2198ce 100644
> --- a/net/nfc/nci/core.c
> +++ b/net/nfc/nci/core.c
> @@ -70,14 +70,13 @@ int nci_get_conn_info_by_dest_type_params(struct nci_dev *ndev, u8 dest_type,
>  	struct nci_conn_info *conn_info;
>  
>  	list_for_each_entry(conn_info, &ndev->conn_info_list, list) {

conn_info is set in list_for_each_entry() using container_of(),
which is never NULL. Plus, it is dereferenced there as well.
The check is unnecessary.

Guenter

> -		if (conn_info->dest_type == dest_type) {
> +		if (conn_info && conn_info->dest_type == dest_type) {
>  			if (!params)
>  				return conn_info->conn_id;
> -			if (conn_info) {
> -				if (params->id == conn_info->dest_params->id &&
> -				    params->protocol == conn_info->dest_params->protocol)
> -					return conn_info->conn_id;
> -			}
> +
> +			if (params->id == conn_info->dest_params->id &&
> +			    params->protocol == conn_info->dest_params->protocol)
> +				return conn_info->conn_id;
>  		}
>  	}
>