From: Florian Westphal <fw@strlen•de>
To: <netdev@vger•kernel.org>
Cc: Florian Westphal <fw@strlen•de>
Subject: [PATCH v2 net-next 3/7] rtnetlink: add reference counting to prevent module unload while dump is in progress
Date: Wed, 9 Aug 2017 20:41:49 +0200 [thread overview]
Message-ID: <20170809184153.16700-4-fw@strlen.de> (raw)
In-Reply-To: <20170809184153.16700-1-fw@strlen.de>
I don't see what prevents rmmod (unregister_all is called) while a dump
is active.
Even if we'd add rtnl lock/unlock pair to unregister_all (as done here),
thats not enough either as rtnl_lock is released right before the dump
process starts.
So this adds a refcount:
* acquire rtnl mutex
* bump refcount
* release mutex
* start the dump
... and make unregister_all remove the callbacks (no new dumps possible)
and then wait until refcount is 0.
Signed-off-by: Florian Westphal <fw@strlen•de>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion•org>
---
No changes since v1.
net/core/rtnetlink.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 67607c540c03..c45a7c5e3232 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -127,6 +127,7 @@ EXPORT_SYMBOL(lockdep_rtnl_is_held);
#endif /* #ifdef CONFIG_PROVE_LOCKING */
static struct rtnl_link *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)
{
@@ -272,10 +273,18 @@ EXPORT_SYMBOL_GPL(rtnl_unregister);
*/
void rtnl_unregister_all(int protocol)
{
+ struct rtnl_link *handlers;
+
BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);
- kfree(rtnl_msg_handlers[protocol]);
+ rtnl_lock();
+ handlers = rtnl_msg_handlers[protocol];
rtnl_msg_handlers[protocol] = NULL;
+ rtnl_unlock();
+
+ while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 0)
+ schedule();
+ kfree(handlers);
}
EXPORT_SYMBOL_GPL(rtnl_unregister_all);
@@ -4173,6 +4182,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
if (dumpit == NULL)
return -EOPNOTSUPP;
+ refcount_inc(&rtnl_msg_handlers_ref[family]);
+
if (type == RTM_GETLINK)
min_dump_alloc = rtnl_calcit(skb, nlh);
@@ -4186,6 +4197,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
err = netlink_dump_start(rtnl, skb, nlh, &c);
}
rtnl_lock();
+ refcount_dec(&rtnl_msg_handlers_ref[family]);
return err;
}
--
2.13.0
next prev parent reply other threads:[~2017-08-09 18:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-09 18:41 [PATCH v2 net-next 0/7] rtnetlink: allow selected handlers to run without rtnl Florian Westphal
2017-08-09 18:41 ` [PATCH v2 net-next 1/7] rtnetlink: call rtnl_calcit directly Florian Westphal
2017-08-09 18:41 ` [PATCH v2 net-next 2/7] rtnetlink: make rtnl_register accept a flags parameter Florian Westphal
2017-08-09 18:41 ` Florian Westphal [this message]
2017-08-09 18:41 ` [PATCH v2 net-next 4/7] rtnetlink: small rtnl lock pushdown Florian Westphal
2017-08-09 18:41 ` [PATCH v2 net-next 5/7] rtnetlink: protect handler table with rcu Florian Westphal
2017-08-10 8:26 ` Ido Schimmel
2017-08-09 18:41 ` [PATCH v2 net-next 6/7] rtnetlink: add RTNL_FLAG_DOIT_UNLOCKED Florian Westphal
2017-08-09 18:41 ` [PATCH v2 net-next 7/7] net: call newid/getid without rtnl mutex held Florian Westphal
2017-08-10 0:21 ` [PATCH v2 net-next 0/7] rtnetlink: allow selected handlers to run without rtnl David Miller
2017-08-10 1:27 ` David Ahern
2017-08-10 11:29 ` Florian Westphal
2017-08-10 16:23 ` David Ahern
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