From: Eric Dumazet <edumazet@google.com> mainline inclusion from mainline-v6.9-rc1 commit 223f55196bbdb182a9b8de6108a0834b5e5e832e category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/ICITYB CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------------------------------------- inet_diag_lock_handler() current implementation uses a mutex to protect inet_diag_table[] array against concurrent changes. This makes inet_diag dump serialized, thus less scalable than legacy /proc files. It is time to switch to full RCU protection. As a bonus, if a target is statically linked instead of being modular, inet_diag_lock_handler() & inet_diag_unlock_handler() reduce to reads only. Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Guillaume Nault <gnault@redhat.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Liu Jian <liujian56@huawei.com> --- net/ipv4/inet_diag.c | 80 ++++++++++++++++++++++---------------------- 1 file changed, 40 insertions(+), 40 deletions(-) diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c index 8383b01746e7..93fea0185725 100644 --- a/net/ipv4/inet_diag.c +++ b/net/ipv4/inet_diag.c @@ -32,7 +32,7 @@ #include <linux/inet_diag.h> #include <linux/sock_diag.h> -static const struct inet_diag_handler **inet_diag_table; +static const struct inet_diag_handler __rcu **inet_diag_table; struct inet_diag_entry { const __be32 *saddr; @@ -48,28 +48,28 @@ struct inet_diag_entry { #endif }; -static DEFINE_MUTEX(inet_diag_table_mutex); - static const struct inet_diag_handler *inet_diag_lock_handler(int proto) { - if (proto < 0 || proto >= IPPROTO_MAX) { - mutex_lock(&inet_diag_table_mutex); - return ERR_PTR(-ENOENT); - } + const struct inet_diag_handler *handler; + + if (proto < 0 || proto >= IPPROTO_MAX) + return NULL; if (!READ_ONCE(inet_diag_table[proto])) sock_load_diag_module(AF_INET, proto); - mutex_lock(&inet_diag_table_mutex); - if (!inet_diag_table[proto]) - return ERR_PTR(-ENOENT); + rcu_read_lock(); + handler = rcu_dereference(inet_diag_table[proto]); + if (handler && !try_module_get(handler->owner)) + handler = NULL; + rcu_read_unlock(); - return inet_diag_table[proto]; + return handler; } static void inet_diag_unlock_handler(const struct inet_diag_handler *handler) { - mutex_unlock(&inet_diag_table_mutex); + module_put(handler->owner); } void inet_diag_msg_common_fill(struct inet_diag_msg *r, struct sock *sk) @@ -104,9 +104,12 @@ static size_t inet_sk_attr_size(struct sock *sk, const struct inet_diag_handler *handler; size_t aux = 0; - handler = inet_diag_table[req->sdiag_protocol]; + rcu_read_lock(); + handler = rcu_dereference(inet_diag_table[req->sdiag_protocol]); + DEBUG_NET_WARN_ON_ONCE(!handler); if (handler && handler->idiag_get_aux_size) aux = handler->idiag_get_aux_size(sk, net_admin); + rcu_read_unlock(); return nla_total_size(sizeof(struct tcp_info)) + nla_total_size(sizeof(struct inet_diag_msg)) @@ -244,10 +247,16 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk, struct nlmsghdr *nlh; struct nlattr *attr; void *info = NULL; + int protocol; cb_data = cb->data; - handler = inet_diag_table[inet_diag_get_protocol(req, cb_data)]; - BUG_ON(!handler); + protocol = inet_diag_get_protocol(req, cb_data); + + /* inet_diag_lock_handler() made sure inet_diag_table[] is stable. */ + handler = rcu_dereference_protected(inet_diag_table[protocol], 1); + DEBUG_NET_WARN_ON_ONCE(!handler); + if (!handler) + return -ENXIO; nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq, cb->nlh->nlmsg_type, sizeof(*r), nlmsg_flags); @@ -605,9 +614,10 @@ static int inet_diag_cmd_exact(int cmd, struct sk_buff *in_skb, protocol = inet_diag_get_protocol(req, &dump_data); handler = inet_diag_lock_handler(protocol); - if (IS_ERR(handler)) { - err = PTR_ERR(handler); - } else if (cmd == SOCK_DIAG_BY_FAMILY) { + if (!handler) + return -ENOENT; + + if (cmd == SOCK_DIAG_BY_FAMILY) { struct netlink_callback cb = { .nlh = nlh, .skb = in_skb, @@ -1175,12 +1185,12 @@ static int __inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, again: prev_min_dump_alloc = cb->min_dump_alloc; handler = inet_diag_lock_handler(protocol); - if (!IS_ERR(handler)) + if (handler) { handler->dump(skb, cb, r); - else - err = PTR_ERR(handler); - inet_diag_unlock_handler(handler); - + inet_diag_unlock_handler(handler); + } else { + err = -ENOENT; + } /* The skb is not large enough to fit one sk info and * inet_sk_diag_fill() has requested for a larger skb. */ @@ -1375,10 +1385,9 @@ int inet_diag_handler_get_info(struct sk_buff *skb, struct sock *sk) } handler = inet_diag_lock_handler(sk->sk_protocol); - if (IS_ERR(handler)) { - inet_diag_unlock_handler(handler); + if (!handler) { nlmsg_cancel(skb, nlh); - return PTR_ERR(handler); + return -ENOENT; } attr = handler->idiag_info_size @@ -1415,20 +1424,12 @@ static const struct sock_diag_handler inet6_diag_handler = { int inet_diag_register(const struct inet_diag_handler *h) { const __u16 type = h->idiag_type; - int err = -EINVAL; if (type >= IPPROTO_MAX) - goto out; + return -EINVAL; - mutex_lock(&inet_diag_table_mutex); - err = -EEXIST; - if (!inet_diag_table[type]) { - WRITE_ONCE(inet_diag_table[type], h); - err = 0; - } - mutex_unlock(&inet_diag_table_mutex); -out: - return err; + return !cmpxchg((const struct inet_diag_handler **)&inet_diag_table[type], + NULL, h) ? 0 : -EEXIST; } EXPORT_SYMBOL_GPL(inet_diag_register); @@ -1439,9 +1440,8 @@ void inet_diag_unregister(const struct inet_diag_handler *h) if (type >= IPPROTO_MAX) return; - mutex_lock(&inet_diag_table_mutex); - WRITE_ONCE(inet_diag_table[type], NULL); - mutex_unlock(&inet_diag_table_mutex); + xchg((const struct inet_diag_handler **)&inet_diag_table[type], + NULL); } EXPORT_SYMBOL_GPL(inet_diag_unregister); -- 2.34.1