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Message-Id: <20200819092436.58232-2-lmb@cloudflare.com>
Date: Wed, 19 Aug 2020 10:24:31 +0100
From: Lorenz Bauer <lmb@...udflare.com>
To: jakub@...udflare.com, john.fastabend@...il.com,
Daniel Borkmann <daniel@...earbox.net>,
Lorenz Bauer <lmb@...udflare.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.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 1/6] net: sk_msg: simplify sk_psock initialization
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 <lmb@...udflare.com>
---
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];
}
--
2.25.1
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