Re: [PATCH net] netlink: fix wrong subscription bitmask to group mapping in

[Ivan Delalande <colona@arista.com>]

On Thu, Jan 29, 2015 at 10:51:53AM +0100, Pablo Neira Ayuso wrote:
> The subscription bitmask passed via struct sockaddr_nl is converted to
> the group number when calling the netlink_bind() and netlink_unbind()
> callbacks.
> 
> The conversion is however incorrect since bitmask (1 << 0) needs to be
> mapped to group number 1. Note that you cannot specify the group number 0
> (usually known as _NONE) from setsockopt() using NETLINK_ADD_MEMBERSHIP
> since this is rejected through -EINVAL.
> 
> This problem became noticeable since 97840cb ("netfilter: nfnetlink:
> fix insufficient validation in nfnetlink_bind") when binding to bitmask
> (1 << 0) in ctnetlink.
> 
> Reported-by: Andre Tomt <andre@tomt.net>
> Reported-by: Ivan Delalande <colona@arista.com>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Thanks a lot for this fix!

> ---
> v2: Rebased upon current net tree. Previous patch:
> 
> http://patchwork.ozlabs.org/patch/426205/
> 
> did not apply cleanly.
> 
>  net/netlink/af_netlink.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 02fdde2..75532ef 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -1438,7 +1438,7 @@ static void netlink_undo_bind(int group, long unsigned int groups,
>  
>  	for (undo = 0; undo < group; undo++)
>  		if (test_bit(undo, &groups))
> -			nlk->netlink_unbind(sock_net(sk), undo);
> +			nlk->netlink_unbind(sock_net(sk), undo + 1);
>  }
>  
>  static int netlink_bind(struct socket *sock, struct sockaddr *addr,
> @@ -1476,7 +1476,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
>  		for (group = 0; group < nlk->ngroups; group++) {
>  			if (!test_bit(group, &groups))
>  				continue;
> -			err = nlk->netlink_bind(net, group);
> +			err = nlk->netlink_bind(net, group + 1);
>  			if (!err)
>  				continue;
>  			netlink_undo_bind(group, groups, sk);

I guess this should also be group + 1 there:

	netlink_undo_bind(group + 1, groups, sk);

-- 
Ivan "Colona" Delalande
Arista Networks