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rtnetlink: Protect struct rtnl_link_ops with SRCU.

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Once RTNL is replaced with rtnl_net_lock(), we need a mechanism to
guarantee that rtnl_link_ops is alive during inflight RTM_NEWLINK
even when its module is being unloaded.

Let's use SRCU to protect ops.

rtnl_link_ops_get() now iterates link_ops under RCU and returns
SRCU-protected ops pointer.  The caller must call rtnl_link_ops_put()
to release the pointer after the use.

Also, __rtnl_link_unregister() unlinks the ops first and calls
synchronize_srcu() to wait for inflight RTM_NEWLINK requests to
complete.

Note that link_ops needs to be protected by its dedicated lock
when RTNL is removed.

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2024-10-16 11:53:50 -07:00 committed by Paolo Abeni
parent 0d3008d1a9
commit 43c7ce69d2
2 changed files with 65 additions and 23 deletions
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5
include/net/rtnetlink.h
View File

@ -3,6 +3,7 @@
#define __NET_RTNETLINK_H
#include <linux/rtnetlink.h>
#include <linux/srcu.h>
#include <net/netlink.h>
typedef int (*rtnl_doit_func)(struct sk_buff *, struct nlmsghdr *,
@ -69,7 +70,8 @@ static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
/**
* struct rtnl_link_ops - rtnetlink link operations
*
* @list: Used internally
* @list: Used internally, protected by RTNL and SRCU
* @srcu: Used internally
* @kind: Identifier
* @netns_refund: Physical device, move to init_net on netns exit
* @maxtype: Highest device specific netlink attribute number
@ -100,6 +102,7 @@ static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
*/
struct rtnl_link_ops {
struct list_head list;
struct srcu_struct srcu;
const char *kind;

83
net/core/rtnetlink.c
View File

@ -457,15 +457,29 @@ EXPORT_SYMBOL_GPL(__rtnl_unregister_many);
static LIST_HEAD(link_ops);
static const struct rtnl_link_ops *rtnl_link_ops_get(const char *kind)
static struct rtnl_link_ops *rtnl_link_ops_get(const char *kind, int *srcu_index)
{
const struct rtnl_link_ops *ops;
struct rtnl_link_ops *ops;
list_for_each_entry(ops, &link_ops, list) {
if (!strcmp(ops->kind, kind))
return ops;
rcu_read_lock();
list_for_each_entry_rcu(ops, &link_ops, list) {
if (!strcmp(ops->kind, kind)) {
*srcu_index = srcu_read_lock(&ops->srcu);
goto unlock;
}
}
return NULL;
ops = NULL;
unlock:
rcu_read_unlock();
return ops;
}
static void rtnl_link_ops_put(struct rtnl_link_ops *ops, int srcu_index)
{
srcu_read_unlock(&ops->srcu, srcu_index);
}
/**
@ -480,8 +494,16 @@ static const struct rtnl_link_ops *rtnl_link_ops_get(const char *kind)
*/
int __rtnl_link_register(struct rtnl_link_ops *ops)
{
if (rtnl_link_ops_get(ops->kind))
return -EEXIST;
struct rtnl_link_ops *tmp;
int err;
/* When RTNL is removed, add lock for link_ops. */
ASSERT_RTNL();
list_for_each_entry(tmp, &link_ops, list) {
if (!strcmp(ops->kind, tmp->kind))
return -EEXIST;
}
/* The check for alloc/setup is here because if ops
* does not have that filled up, it is not possible
@ -491,7 +513,12 @@ int __rtnl_link_register(struct rtnl_link_ops *ops)
if ((ops->alloc || ops->setup) && !ops->dellink)
ops->dellink = unregister_netdevice_queue;
list_add_tail(&ops->list, &link_ops);
err = init_srcu_struct(&ops->srcu);
if (err)
return err;
list_add_tail_rcu(&ops->list, &link_ops);
return 0;
}
EXPORT_SYMBOL_GPL(__rtnl_link_register);
@ -542,10 +569,12 @@ void __rtnl_link_unregister(struct rtnl_link_ops *ops)
{
struct net *net;
for_each_net(net) {
list_del_rcu(&ops->list);
synchronize_srcu(&ops->srcu);
cleanup_srcu_struct(&ops->srcu);
for_each_net(net)
__rtnl_kill_links(net, ops);
}
list_del(&ops->list);
}
EXPORT_SYMBOL_GPL(__rtnl_link_unregister);
@ -2158,10 +2187,11 @@ static const struct nla_policy ifla_xdp_policy[IFLA_XDP_MAX + 1] = {
[IFLA_XDP_PROG_ID] = { .type = NLA_U32 },
};
static const struct rtnl_link_ops *linkinfo_to_kind_ops(const struct nlattr *nla)
static struct rtnl_link_ops *linkinfo_to_kind_ops(const struct nlattr *nla,
int *ops_srcu_index)
{
const struct rtnl_link_ops *ops = NULL;
struct nlattr *linfo[IFLA_INFO_MAX + 1];
struct rtnl_link_ops *ops = NULL;
if (nla_parse_nested_deprecated(linfo, IFLA_INFO_MAX, nla, ifla_info_policy, NULL) < 0)
return NULL;
@ -2170,7 +2200,7 @@ static const struct rtnl_link_ops *linkinfo_to_kind_ops(const struct nlattr *nla
char kind[MODULE_NAME_LEN];
nla_strscpy(kind, linfo[IFLA_INFO_KIND], sizeof(kind));
ops = rtnl_link_ops_get(kind);
ops = rtnl_link_ops_get(kind, ops_srcu_index);
}
return ops;
@ -2290,8 +2320,8 @@ static int rtnl_valid_dump_ifinfo_req(const struct nlmsghdr *nlh,
static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
{
const struct rtnl_link_ops *kind_ops = NULL;
struct netlink_ext_ack *extack = cb->extack;
struct rtnl_link_ops *kind_ops = NULL;
const struct nlmsghdr *nlh = cb->nlh;
struct net *net = sock_net(skb->sk);
unsigned int flags = NLM_F_MULTI;
@ -2302,6 +2332,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
struct net *tgt_net = net;
u32 ext_filter_mask = 0;
struct net_device *dev;
int ops_srcu_index;
int master_idx = 0;
int netnsid = -1;
int err, i;
@ -2335,7 +2366,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
master_idx = nla_get_u32(tb[i]);
break;
case IFLA_LINKINFO:
kind_ops = linkinfo_to_kind_ops(tb[i]);
kind_ops = linkinfo_to_kind_ops(tb[i], &ops_srcu_index);
break;
default:
if (cb->strict_check) {
@ -2361,6 +2392,10 @@ walk_entries:
if (err < 0)
break;
}
if (kind_ops)
rtnl_link_ops_put(kind_ops, ops_srcu_index);
cb->seq = tgt_net->dev_base_seq;
nl_dump_check_consistent(cb, nlmsg_hdr(skb));
if (netnsid >= 0)
@ -3747,8 +3782,9 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct nlattr **tb, **linkinfo, **data = NULL;
const struct rtnl_link_ops *ops = NULL;
struct rtnl_link_ops *ops = NULL;
struct rtnl_newlink_tbs *tbs;
int ops_srcu_index;
int ret;
tbs = kmalloc(sizeof(*tbs), GFP_KERNEL);
@ -3780,13 +3816,13 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
char kind[MODULE_NAME_LEN];
nla_strscpy(kind, linkinfo[IFLA_INFO_KIND], sizeof(kind));
ops = rtnl_link_ops_get(kind);
ops = rtnl_link_ops_get(kind, &ops_srcu_index);
#ifdef CONFIG_MODULES
if (!ops) {
__rtnl_unlock();
request_module("rtnl-link-%s", kind);
rtnl_lock();
ops = rtnl_link_ops_get(kind);
ops = rtnl_link_ops_get(kind, &ops_srcu_index);
}
#endif
}
@ -3800,7 +3836,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
linkinfo[IFLA_INFO_DATA],
ops->policy, extack);
if (ret < 0)
goto free;
goto put_ops;
data = tbs->attr;
}
@ -3808,12 +3844,15 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
if (ops->validate) {
ret = ops->validate(tb, data, extack);
if (ret < 0)
goto free;
goto put_ops;
}
}
ret = __rtnl_newlink(skb, nlh, ops, tbs, data, extack);
put_ops:
if (ops)
rtnl_link_ops_put(ops, ops_srcu_index);
free:
kfree(tbs);
return ret;