netdev - Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for BPF_FLOW_DISSECTOR attach

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f85cf077-aa9e-775f-f3e7-1538354514cd@iogearbox.net>
Date:   Thu, 25 Apr 2019 23:21:29 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     davem@...emloft.net, ast@...nel.org, jakub.kicinski@...ronome.com,
        quentin.monnet@...ronome.com, Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for
 BPF_FLOW_DISSECTOR attach_type

On 04/24/2019 11:31 PM, Stanislav Fomichev wrote:
> target_fd is target namespace. If there is a flow dissector BPF program
> attached to that namespace, its (single) id is returned.
> 
> v4:
> * add missing put_net (Jann Horn)
> 
> v3:
> * add missing inline to skb_flow_dissector_prog_query static def
>   (kbuild test robot <lkp@...el.com>)
> 
> v2:
> * don't sleep in rcu critical section (Jakub Kicinski)
> * check input prog_cnt (exit early)
> 
> Cc: Jann Horn <jannh@...gle.com>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  include/linux/skbuff.h    |  8 +++++++
>  kernel/bpf/syscall.c      |  2 ++
>  net/core/flow_dissector.c | 46 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 56 insertions(+)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 998256c2820b..6d58fa8a65fd 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1258,11 +1258,19 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
>  			     unsigned int key_count);
>  
>  #ifdef CONFIG_NET
> +int skb_flow_dissector_prog_query(const union bpf_attr *attr,
> +				  union bpf_attr __user *uattr);
>  int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
>  				       struct bpf_prog *prog);
>  
>  int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr);
>  #else
> +static inline int skb_flow_dissector_prog_query(const union bpf_attr *attr,
> +						union bpf_attr __user *uattr)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  static inline int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
>  						     struct bpf_prog *prog)
>  {
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 92c9b8a32b50..b0de49598341 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2009,6 +2009,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
>  		break;
>  	case BPF_LIRC_MODE2:
>  		return lirc_prog_query(attr, uattr);
> +	case BPF_FLOW_DISSECTOR:
> +		return skb_flow_dissector_prog_query(attr, uattr);
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index fac712cee9d5..27466e54ad3a 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -65,6 +65,52 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
>  }
>  EXPORT_SYMBOL(skb_flow_dissector_init);
>  
> +int skb_flow_dissector_prog_query(const union bpf_attr *attr,
> +				  union bpf_attr __user *uattr)
> +{
> +	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
> +	u32 prog_id, prog_cnt = 0, flags = 0;
> +	struct bpf_prog *attached;
> +	struct net *net;
> +	int ret = 0;
> +
> +	if (attr->query.query_flags)
> +		return -EINVAL;
> +
> +	net = get_net_ns_by_fd(attr->query.target_fd);
> +	if (IS_ERR(net))
> +		return PTR_ERR(net);
> +
> +	rcu_read_lock();
> +	attached = rcu_dereference(net->flow_dissector_prog);
> +	if (attached) {
> +		prog_cnt = 1;
> +		prog_id = attached->aux->id;
> +	}
> +	rcu_read_unlock();

Patch looks good to me, one small nit: is there any reason you didn't
do the put_net(net) right after the rcu_read_unlock() above? Below it's
not really needed anymore, so this would also simplify the error paths
by being able to directly return in error case, no?

> +	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
> +		goto out;
> +
> +	if (copy_to_user(prog_ids, &prog_id, sizeof(u32))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +out:
> +	put_net(net);
> +	return ret;
> +}
> +
>  int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
>  				       struct bpf_prog *prog)
>  {
>