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inet_diag: allow concurrent operations

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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>
This commit is contained in:
Eric Dumazet 2024-01-22 11:25:58 +00:00 committed by Paolo Abeni
parent db5914695a
commit 223f55196b
1 changed files with 40 additions and 40 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

80
net/ipv4/inet_diag.c
View file

@ -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,
@ -1259,12 +1269,12 @@ 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.
*/
@ -1457,10 +1467,9 @@ 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
@ -1495,20 +1504,12 @@ 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);
@ -1519,9 +1520,8 @@ 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);