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[2001:8b0:7a5a:26ff:60d6:619e:3324:40dc]) by smtp.gmail.com with ESMTPSA id 3sm4204565wms.36.2020.08.19.02.37.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Aug 2020 02:37:45 -0700 (PDT) From: Lorenz Bauer To: jakub@cloudflare.com, john.fastabend@gmail.com, Daniel Borkmann , Lorenz Bauer , "David S. Miller" , Jakub Kicinski , Eric Dumazet , Alexey Kuznetsov , Hideaki YOSHIFUJI , Alexei Starovoitov Cc: kernel-team@cloudflare.com, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next 1/6] net: sk_msg: simplify sk_psock initialization Date: Wed, 19 Aug 2020 10:24:31 +0100 Message-Id: <20200819092436.58232-2-lmb@cloudflare.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200819092436.58232-1-lmb@cloudflare.com> References: <20200819092436.58232-1-lmb@cloudflare.com> MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Initializing psock->sk_proto and other saved callbacks is only done in sk_psock_update_proto, after sk_psock_init has returned. The logic for this is difficult to follow, and needlessly complex. Instead, initialize psock->sk_proto whenever we allocate a new psock. Additionally, assert the following invariants: * The SK has no ULP: ULP does it's own finagling of sk->sk_prot * sk_user_data is unused: we need it to store sk_psock Protect our access to sk_user_data with sk_callback_lock, which is what other users like reuseport arrays, etc. do. The result is that an sk_psock is always fully initialized, and that psock->sk_proto is always the "original" struct proto. The latter allows us to use psock->sk_proto when initializing IPv6 TCP / UDP callbacks for sockmap. Signed-off-by: Lorenz Bauer --- include/linux/skmsg.h | 17 ----------------- net/core/skmsg.c | 34 ++++++++++++++++++++++++++++------ net/core/sock_map.c | 14 ++++---------- net/ipv4/tcp_bpf.c | 13 +++++-------- net/ipv4/udp_bpf.c | 9 ++++----- 5 files changed, 41 insertions(+), 46 deletions(-) diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h index 1e9ed840b9fc..3119928fc103 100644 --- a/include/linux/skmsg.h +++ b/include/linux/skmsg.h @@ -340,23 +340,6 @@ static inline void sk_psock_update_proto(struct sock *sk, struct sk_psock *psock, struct proto *ops) { - /* Initialize saved callbacks and original proto only once, since this - * function may be called multiple times for a psock, e.g. when - * psock->progs.msg_parser is updated. - * - * Since we've not installed the new proto, psock is not yet in use and - * we can initialize it without synchronization. - */ - if (!psock->sk_proto) { - struct proto *orig = READ_ONCE(sk->sk_prot); - - psock->saved_unhash = orig->unhash; - psock->saved_close = orig->close; - psock->saved_write_space = sk->sk_write_space; - - psock->sk_proto = orig; - } - /* Pairs with lockless read in sk_clone_lock() */ WRITE_ONCE(sk->sk_prot, ops); } diff --git a/net/core/skmsg.c b/net/core/skmsg.c index 6a32a1fd34f8..1c81caf9630f 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -494,14 +494,34 @@ static void sk_psock_backlog(struct work_struct *work) struct sk_psock *sk_psock_init(struct sock *sk, int node) { - struct sk_psock *psock = kzalloc_node(sizeof(*psock), - GFP_ATOMIC | __GFP_NOWARN, - node); - if (!psock) - return NULL; + struct sk_psock *psock; + struct proto *prot; + write_lock_bh(&sk->sk_callback_lock); + + if (inet_csk_has_ulp(sk)) { + psock = ERR_PTR(-EINVAL); + goto out; + } + + if (sk->sk_user_data) { + psock = ERR_PTR(-EBUSY); + goto out; + } + + psock = kzalloc_node(sizeof(*psock), GFP_ATOMIC | __GFP_NOWARN, node); + if (!psock) { + psock = ERR_PTR(-ENOMEM); + goto out; + } + + prot = READ_ONCE(sk->sk_prot); psock->sk = sk; - psock->eval = __SK_NONE; + psock->eval = __SK_NONE; + psock->sk_proto = prot; + psock->saved_unhash = prot->unhash; + psock->saved_close = prot->close; + psock->saved_write_space = sk->sk_write_space; INIT_LIST_HEAD(&psock->link); spin_lock_init(&psock->link_lock); @@ -516,6 +536,8 @@ struct sk_psock *sk_psock_init(struct sock *sk, int node) rcu_assign_sk_user_data_nocopy(sk, psock); sock_hold(sk); +out: + write_unlock_bh(&sk->sk_callback_lock); return psock; } EXPORT_SYMBOL_GPL(sk_psock_init); diff --git a/net/core/sock_map.c b/net/core/sock_map.c index 119f52a99dc1..abe4bac40db9 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -184,8 +184,6 @@ static int sock_map_init_proto(struct sock *sk, struct sk_psock *psock) { struct proto *prot; - sock_owned_by_me(sk); - switch (sk->sk_type) { case SOCK_STREAM: prot = tcp_bpf_get_proto(sk, psock); @@ -272,8 +270,8 @@ static int sock_map_link(struct bpf_map *map, struct sk_psock_progs *progs, } } else { psock = sk_psock_init(sk, map->numa_node); - if (!psock) { - ret = -ENOMEM; + if (IS_ERR(psock)) { + ret = PTR_ERR(psock); goto out_progs; } } @@ -322,8 +320,8 @@ static int sock_map_link_no_progs(struct bpf_map *map, struct sock *sk) if (!psock) { psock = sk_psock_init(sk, map->numa_node); - if (!psock) - return -ENOMEM; + if (IS_ERR(psock)) + return PTR_ERR(psock); } ret = sock_map_init_proto(sk, psock); @@ -478,8 +476,6 @@ static int sock_map_update_common(struct bpf_map *map, u32 idx, return -EINVAL; if (unlikely(idx >= map->max_entries)) return -E2BIG; - if (inet_csk_has_ulp(sk)) - return -EINVAL; link = sk_psock_init_link(); if (!link) @@ -855,8 +851,6 @@ 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 (inet_csk_has_ulp(sk)) - return -EINVAL; link = sk_psock_init_link(); if (!link) diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 7aa68f4aae6c..37f4cb2bba5c 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -567,10 +567,9 @@ static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS], prot[TCP_BPF_TX].sendpage = tcp_bpf_sendpage; } -static void tcp_bpf_check_v6_needs_rebuild(struct sock *sk, struct proto *ops) +static void tcp_bpf_check_v6_needs_rebuild(struct proto *ops) { - if (sk->sk_family == AF_INET6 && - unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) { + if (unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) { spin_lock_bh(&tcpv6_prot_lock); if (likely(ops != tcpv6_prot_saved)) { tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV6], ops); @@ -603,13 +602,11 @@ struct proto *tcp_bpf_get_proto(struct sock *sk, struct sk_psock *psock) int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4; int config = psock->progs.msg_parser ? TCP_BPF_TX : TCP_BPF_BASE; - if (!psock->sk_proto) { - struct proto *ops = READ_ONCE(sk->sk_prot); - - if (tcp_bpf_assert_proto_ops(ops)) + if (sk->sk_family == AF_INET6) { + if (tcp_bpf_assert_proto_ops(psock->sk_proto)) return ERR_PTR(-EINVAL); - tcp_bpf_check_v6_needs_rebuild(sk, ops); + tcp_bpf_check_v6_needs_rebuild(psock->sk_proto); } return &tcp_bpf_prots[family][config]; diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c index eddd973e6575..7a94791efc1a 100644 --- a/net/ipv4/udp_bpf.c +++ b/net/ipv4/udp_bpf.c @@ -22,10 +22,9 @@ static void udp_bpf_rebuild_protos(struct proto *prot, const struct proto *base) prot->close = sock_map_close; } -static void udp_bpf_check_v6_needs_rebuild(struct sock *sk, struct proto *ops) +static void udp_bpf_check_v6_needs_rebuild(struct proto *ops) { - if (sk->sk_family == AF_INET6 && - unlikely(ops != smp_load_acquire(&udpv6_prot_saved))) { + if (unlikely(ops != smp_load_acquire(&udpv6_prot_saved))) { spin_lock_bh(&udpv6_prot_lock); if (likely(ops != udpv6_prot_saved)) { udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV6], ops); @@ -46,8 +45,8 @@ struct proto *udp_bpf_get_proto(struct sock *sk, struct sk_psock *psock) { int family = sk->sk_family == AF_INET ? UDP_BPF_IPV4 : UDP_BPF_IPV6; - if (!psock->sk_proto) - udp_bpf_check_v6_needs_rebuild(sk, READ_ONCE(sk->sk_prot)); + if (sk->sk_family == AF_INET6) + udp_bpf_check_v6_needs_rebuild(psock->sk_proto); return &udp_bpf_prots[family]; }