netdev - Re: [PATCH v3] netlink: fix null pointer dereference on nlk->groups

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Message-ID: <CAOJe8K10a=MLyZwFCYvstP+KG3bND09RjbXVZDR5gWfFxCvMcg@mail.gmail.com>
Date:	Tue, 12 Jan 2016 14:15:54 +0300
From:	Denis Kirjanov <kda@...ux-powerpc.org>
To:	Baozeng Ding <sploving1@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH v3] netlink: fix null pointer dereference on nlk->groups

On 1/12/16, Baozeng Ding <sploving1@...il.com> wrote:
> If groups is not 0 and nlk->groups is NULL, it will not return
> immediately and cause a null pointer dereference later.
>
> Signed-off-by: Baozeng Ding <sploving1@...il.com>
> ---
> The v3 version adds WARN_ON, suggested by David Miller. Thanks for
> David's feedback.

But can you explain how can we get to this situation?

> ---
>  net/netlink/af_netlink.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 59651af..f93d579 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -1576,7 +1576,10 @@ static int netlink_bind(struct socket *sock, struct
> sockaddr *addr,
>  		}
>  	}
>
> -	if (!groups && (nlk->groups == NULL || !(u32)nlk->groups[0]))
> +	if (WARN_ON(!nlk->groups))
> +		return 0;
> +
> +	if (!groups && !(u32)nlk->groups[0])
>  		return 0;
>
>  	netlink_table_grab();
> --
> 1.9.1
>
>