rtnetlink: get reference on module before invoking handlers
Add yet another rtnl_register function. It will be used by modules
that can be removed.
The passed module struct is used to prevent module unload while
a netlink dump is in progress or when a DOIT_UNLOCKED doit callback
is called.
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index ead01874..e326b3f 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -17,6 +17,8 @@
rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);
void rtnl_register(int protocol, int msgtype,
rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);
+int rtnl_register_module(struct module *owner, int protocol, int msgtype,
+ rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);
int rtnl_unregister(int protocol, int msgtype);
void rtnl_unregister_all(int protocol);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index ff292d3..de63903 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -62,6 +62,7 @@
struct rtnl_link {
rtnl_doit_func doit;
rtnl_dumpit_func dumpit;
+ struct module *owner;
unsigned int flags;
struct rcu_head rcu;
};
@@ -129,7 +130,6 @@
#endif /* #ifdef CONFIG_PROVE_LOCKING */
static struct rtnl_link __rcu **rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];
-static refcount_t rtnl_msg_handlers_ref[RTNL_FAMILY_MAX + 1];
static inline int rtm_msgindex(int msgtype)
{
@@ -159,27 +159,10 @@
return tab[msgtype];
}
-/**
- * __rtnl_register - Register a rtnetlink message type
- * @protocol: Protocol family or PF_UNSPEC
- * @msgtype: rtnetlink message type
- * @doit: Function pointer called for each request message
- * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message
- * @flags: rtnl_link_flags to modifiy behaviour of doit/dumpit functions
- *
- * Registers the specified function pointers (at least one of them has
- * to be non-NULL) to be called whenever a request message for the
- * specified protocol family and message type is received.
- *
- * The special protocol family PF_UNSPEC may be used to define fallback
- * function pointers for the case when no entry for the specific protocol
- * family exists.
- *
- * Returns 0 on success or a negative error code.
- */
-int __rtnl_register(int protocol, int msgtype,
- rtnl_doit_func doit, rtnl_dumpit_func dumpit,
- unsigned int flags)
+static int rtnl_register_internal(struct module *owner,
+ int protocol, int msgtype,
+ rtnl_doit_func doit, rtnl_dumpit_func dumpit,
+ unsigned int flags)
{
struct rtnl_link **tab, *link, *old;
int msgindex;
@@ -210,6 +193,9 @@
goto unlock;
}
+ WARN_ON(link->owner && link->owner != owner);
+ link->owner = owner;
+
WARN_ON(doit && link->doit && link->doit != doit);
if (doit)
link->doit = doit;
@@ -228,6 +214,54 @@
rtnl_unlock();
return ret;
}
+
+/**
+ * rtnl_register_module - Register a rtnetlink message type
+ *
+ * @owner: module registering the hook (THIS_MODULE)
+ * @protocol: Protocol family or PF_UNSPEC
+ * @msgtype: rtnetlink message type
+ * @doit: Function pointer called for each request message
+ * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message
+ * @flags: rtnl_link_flags to modifiy behaviour of doit/dumpit functions
+ *
+ * Like rtnl_register, but for use by removable modules.
+ */
+int rtnl_register_module(struct module *owner,
+ int protocol, int msgtype,
+ rtnl_doit_func doit, rtnl_dumpit_func dumpit,
+ unsigned int flags)
+{
+ return rtnl_register_internal(owner, protocol, msgtype,
+ doit, dumpit, flags);
+}
+EXPORT_SYMBOL_GPL(rtnl_register_module);
+
+/**
+ * __rtnl_register - Register a rtnetlink message type
+ * @protocol: Protocol family or PF_UNSPEC
+ * @msgtype: rtnetlink message type
+ * @doit: Function pointer called for each request message
+ * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message
+ * @flags: rtnl_link_flags to modifiy behaviour of doit/dumpit functions
+ *
+ * Registers the specified function pointers (at least one of them has
+ * to be non-NULL) to be called whenever a request message for the
+ * specified protocol family and message type is received.
+ *
+ * The special protocol family PF_UNSPEC may be used to define fallback
+ * function pointers for the case when no entry for the specific protocol
+ * family exists.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int __rtnl_register(int protocol, int msgtype,
+ rtnl_doit_func doit, rtnl_dumpit_func dumpit,
+ unsigned int flags)
+{
+ return rtnl_register_internal(NULL, protocol, msgtype,
+ doit, dumpit, flags);
+}
EXPORT_SYMBOL_GPL(__rtnl_register);
/**
@@ -311,8 +345,6 @@
synchronize_net();
- while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 1)
- schedule();
kfree(tab);
}
EXPORT_SYMBOL_GPL(rtnl_unregister_all);
@@ -4372,6 +4404,7 @@
{
struct net *net = sock_net(skb->sk);
struct rtnl_link *link;
+ struct module *owner;
int err = -EOPNOTSUPP;
rtnl_doit_func doit;
unsigned int flags;
@@ -4408,24 +4441,32 @@
if (!link || !link->dumpit)
goto err_unlock;
}
+ owner = link->owner;
dumpit = link->dumpit;
- refcount_inc(&rtnl_msg_handlers_ref[family]);
-
if (type == RTM_GETLINK - RTM_BASE)
min_dump_alloc = rtnl_calcit(skb, nlh);
+ err = 0;
+ /* need to do this before rcu_read_unlock() */
+ if (!try_module_get(owner))
+ err = -EPROTONOSUPPORT;
+
rcu_read_unlock();
rtnl = net->rtnl;
- {
+ if (err == 0) {
struct netlink_dump_control c = {
.dump = dumpit,
.min_dump_alloc = min_dump_alloc,
+ .module = owner,
};
err = netlink_dump_start(rtnl, skb, nlh, &c);
+ /* netlink_dump_start() will keep a reference on
+ * module if dump is still in progress.
+ */
+ module_put(owner);
}
- refcount_dec(&rtnl_msg_handlers_ref[family]);
return err;
}
@@ -4437,14 +4478,19 @@
goto out_unlock;
}
+ owner = link->owner;
+ if (!try_module_get(owner)) {
+ err = -EPROTONOSUPPORT;
+ goto out_unlock;
+ }
+
flags = link->flags;
if (flags & RTNL_FLAG_DOIT_UNLOCKED) {
- refcount_inc(&rtnl_msg_handlers_ref[family]);
doit = link->doit;
rcu_read_unlock();
if (doit)
err = doit(skb, nlh, extack);
- refcount_dec(&rtnl_msg_handlers_ref[family]);
+ module_put(owner);
return err;
}
rcu_read_unlock();
@@ -4455,6 +4501,8 @@
err = link->doit(skb, nlh, extack);
rtnl_unlock();
+ module_put(owner);
+
return err;
out_unlock:
@@ -4546,11 +4594,6 @@
void __init rtnetlink_init(void)
{
- int i;
-
- for (i = 0; i < ARRAY_SIZE(rtnl_msg_handlers_ref); i++)
- refcount_set(&rtnl_msg_handlers_ref[i], 1);
-
if (register_pernet_subsys(&rtnetlink_net_ops))
panic("rtnetlink_init: cannot initialize rtnetlink\n");