[PATCH v2 net-next 3/7] rtnetlink: add reference counting to prevent module unload while dump is in progress
flat view
STALE3354d
REVIEWED: 1 (0M)
From: Florian Westphal <fw@strlen.de>
Date: 2017-08-09 18:41:50
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
1 review trailer.
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 <redacted> --- 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