netdev - Re: [PATCH] net: bridge: fix potential NULL pointer dereference

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Date:   Tue, 6 Jun 2017 01:05:18 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        roopa <roopa@...ulusnetworks.com>
Subject: Re: [PATCH] net: bridge: fix potential NULL pointer dereference

On 06/06/17 00:30, Gustavo A. R. Silva wrote:
> Add NULL check before dereferencing pointer _p_ inside br_afspec().
> 
> Addresses-Coverity-ID: 1401872
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> ---
>  net/bridge/br_netlink.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 1e63ec4..ad85a9c 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -776,7 +776,7 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh, u16 flags)
>  			goto out;
>  	}
>  
> -	if (afspec) {
> +	if (p && afspec) {
>  		err = br_afspec((struct net_bridge *)netdev_priv(dev), p,
>  				afspec, RTM_SETLINK);
>  	}
> 

While I see a possible issue with the new bridge tunnel code (+CC Roopa), this is 
the wrong fix because there are legitimate use cases where p is null and br_afspec
is called.
We need to change the p->flags check in br_afspec()'s IFLA_BRIDGE_VLAN_TUNNEL_INFO case
to check for a NULL p first.

Thanks for the report!