RE: [PATCH bpf-next v2 1/9] bpf: sockmap: only check ULP for TCP sockets

From: John Fastabend <john.fastabend@gmail.com>
To: Lorenz Bauer <lmb@cloudflare.com>,
	john.fastabend@gmail.com, Daniel Borkmann <daniel@iogearbox.net>,
	Jakub Sitnicki <jakub@cloudflare.com>,
	Lorenz Bauer <lmb@cloudflare.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>
Cc: kernel-team@cloudflare.com, netdev@vger.kernel.org,
	bpf@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: RE: [PATCH bpf-next v2 1/9] bpf: sockmap: only check ULP for TCP sockets
Date: Tue, 03 Mar 2020 09:35:22 -0800	[thread overview]
Message-ID: <5e5e955a27139_60e72b06ba14c5bc67@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20200228115344.17742-2-lmb@cloudflare.com>

Lorenz Bauer wrote:
> The sock map code checks that a socket does not have an active upper
> layer protocol before inserting it into the map. This requires casting
> via inet_csk, which isn't valid for UDP sockets.
> 
> Guard checks for ULP by checking inet_sk(sk)->is_icsk first.
> 
> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
> ---
>  include/linux/skmsg.h |  8 +++++++-
>  net/core/sock_map.c   | 11 +++++++----
>  2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
> index 112765bd146d..54a9a3e36b29 100644
> --- a/include/linux/skmsg.h
> +++ b/include/linux/skmsg.h
> @@ -360,7 +360,13 @@ static inline void sk_psock_restore_proto(struct sock *sk,
>  					  struct sk_psock *psock)
>  {
>  	sk->sk_prot->unhash = psock->saved_unhash;
> -	tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
> +	if (inet_sk(sk)->is_icsk) {

use sock_map_sk_has_ulp() here as well and then drop the !icsk->icsk_ulp_ops
case in tcp_update_ulp()?

> +		tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
> +	} else {
> +		sk->sk_write_space = psock->saved_write_space;
> +		/* Pairs with lockless read in sk_clone_lock() */
> +		WRITE_ONCE(sk->sk_prot, psock->sk_proto);
> +	}
>  }
>  
>  static inline void sk_psock_set_state(struct sk_psock *psock,
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 2e0f465295c3..695ecacc7afa 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -94,6 +94,11 @@ static void sock_map_sk_release(struct sock *sk)
>  	release_sock(sk);
>  }
>  
> +static bool sock_map_sk_has_ulp(struct sock *sk)
> +{
> +	return inet_sk(sk)->is_icsk && !!inet_csk(sk)->icsk_ulp_ops;
> +}
> +
>  static void sock_map_add_link(struct sk_psock *psock,
>  			      struct sk_psock_link *link,
>  			      struct bpf_map *map, void *link_raw)
> @@ -384,7 +389,6 @@ static int sock_map_update_common(struct bpf_map *map, u32 idx,
>  				  struct sock *sk, u64 flags)
>  {
>  	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
> -	struct inet_connection_sock *icsk = inet_csk(sk);
>  	struct sk_psock_link *link;
>  	struct sk_psock *psock;
>  	struct sock *osk;
> @@ -395,7 +399,7 @@ static int sock_map_update_common(struct bpf_map *map, u32 idx,
>  		return -EINVAL;
>  	if (unlikely(idx >= map->max_entries))
>  		return -E2BIG;
> -	if (unlikely(rcu_access_pointer(icsk->icsk_ulp_data)))
> +	if (sock_map_sk_has_ulp(sk))
>  		return -EINVAL;
>  
>  	link = sk_psock_init_link();
> @@ -738,7 +742,6 @@ static int sock_hash_update_common(struct bpf_map *map, void *key,
>  				   struct sock *sk, u64 flags)
>  {
>  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
> -	struct inet_connection_sock *icsk = inet_csk(sk);
>  	u32 key_size = map->key_size, hash;
>  	struct bpf_htab_elem *elem, *elem_new;
>  	struct bpf_htab_bucket *bucket;
> @@ -749,7 +752,7 @@ static int sock_hash_update_common(struct bpf_map *map, void *key,
>  	WARN_ON_ONCE(!rcu_read_lock_held());
>  	if (unlikely(flags > BPF_EXIST))
>  		return -EINVAL;
> -	if (unlikely(icsk->icsk_ulp_data))
> +	if (sock_map_sk_has_ulp(sk))
>  		return -EINVAL;
>  
>  	link = sk_psock_init_link();
> -- 
> 2.20.1
> 