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

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Message-Id: <20200228115344.17742-2-lmb@cloudflare.com>
Date:   Fri, 28 Feb 2020 11:53:36 +0000
From:   Lorenz Bauer <lmb@...udflare.com>
To:     john.fastabend@...il.com, Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     kernel-team@...udflare.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 1/9] bpf: sockmap: only check ULP for TCP sockets

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@...udflare.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) {
+		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