Re: [PATCH v2 net-next 1/2] kcm: Only allow TCP sockets to be attached to a KCM mux

[Eric Dumazet <eric.dumazet@gmail.com>]

On Wed, 2018-01-24 at 12:35 -0800, Tom Herbert wrote:
> TCP sockets for IPv4 and IPv6 that are not listeners or in closed
> stated are allowed to be attached to a KCM mux.
> 
> Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
> Reported-by: syzbot+8865eaff7f9acd593945@syzkaller.appspotmail.com
> Signed-off-by: Tom Herbert <tom@quantonium.net>
> ---
>  net/kcm/kcmsock.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
> index d4e98f20fc2a..7632797fb68e 100644
> --- a/net/kcm/kcmsock.c
> +++ b/net/kcm/kcmsock.c
> @@ -1387,8 +1387,13 @@ static int kcm_attach(struct socket *sock, struct socket *csock,
>  	if (!csk)
>  		return -EINVAL;
>  
> -	/* We must prevent loops or risk deadlock ! */
> -	if (csk->sk_family == PF_KCM)
> +	/* Only allow TCP sockets to be attached for now */
> +	if ((csk->sk_family != AF_INET && csk->sk_family != AF_INET6) ||
> +	    csk->sk_protocol != IPPROTO_TCP)
> +		return -EOPNOTSUPP;
> +
> +	/* Don't allow listeners or closed sockets */
> +	if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE)
>  		return -EOPNOTSUPP;
>  
>  	psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL);


Reviewed-by: Eric Dumazet <edumazet@google.com>