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Date: Mon, 6 Nov 2017 11:51:07 +0100
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: peterz@...radead.org, Florian Westphal <fw@...len.de>
Subject: [PATCH net-next 2/8] rtnetlink: add rtnl_register_module
Add yet another rtnl_register function. It will be used by modules
that can be removed.
The passed module struct is used to take a reference while a netlink
dump is in progress to prevent module unload while netlink core can
invoke registered dumper function again.
Signed-off-by: Florian Westphal <fw@...len.de>
---
include/net/rtnetlink.h | 2 +
net/core/rtnetlink.c | 103 +++++++++++++++++++++++++++++++++++++-----------
2 files changed, 83 insertions(+), 22 deletions(-)
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index ead018744ff5..e326b3f9eb5f 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -17,6 +17,8 @@ int __rtnl_register(int protocol, int msgtype,
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 c70f62137dd8..50b483b24845 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;
};
@@ -143,27 +144,10 @@ static inline int rtm_msgindex(int msgtype)
return msgindex;
}
-/**
- * __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;
int msgindex;
@@ -180,6 +164,12 @@ int __rtnl_register(int protocol, int msgtype,
rcu_assign_pointer(rtnl_msg_handlers[protocol], tab);
}
+ WARN_ON(tab[msgindex].owner && tab[msgindex].owner != owner);
+
+ tab[msgindex].owner = owner;
+ /* make sure owner is always visible first */
+ smp_wmb();
+
if (doit)
tab[msgindex].doit = doit;
if (dumpit)
@@ -188,6 +178,60 @@ int __rtnl_register(int protocol, int msgtype,
return 0;
}
+
+/**
+ * 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)
+{
+ int ret;
+
+ rtnl_lock();
+ ret = rtnl_register_internal(owner, protocol, msgtype,
+ doit, dumpit, flags);
+ rtnl_unlock();
+
+ return ret;
+}
+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);
/**
@@ -235,6 +279,9 @@ int rtnl_unregister(int protocol, int msgtype)
handlers[msgindex].doit = NULL;
handlers[msgindex].dumpit = NULL;
handlers[msgindex].flags = 0;
+ /* make sure we clear owner last */
+ smp_wmb();
+ handlers[msgindex].owner = NULL;
rtnl_unlock();
return 0;
@@ -4346,6 +4393,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
}
if (kind == 2 && nlh->nlmsg_flags&NLM_F_DUMP) {
+ struct module *owner = NULL;
struct sock *rtnl;
rtnl_dumpit_func dumpit;
u16 min_dump_alloc = 0;
@@ -4360,20 +4408,31 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
dumpit = READ_ONCE(handlers[type].dumpit);
if (!dumpit)
goto err_unlock;
+ owner = READ_ONCE(handlers[type].owner);
}
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);
}
return err;
}
--
2.13.6
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