Commit 019a3169 authored by Florian Westphal's avatar Florian Westphal Committed by David S. Miller

rtnetlink: add reference counting to prevent module unload while dump is in progress

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: default avatarFlorian Westphal <fw@strlen.de>
Reviewed-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b97bac64
...@@ -127,6 +127,7 @@ EXPORT_SYMBOL(lockdep_rtnl_is_held); ...@@ -127,6 +127,7 @@ EXPORT_SYMBOL(lockdep_rtnl_is_held);
#endif /* #ifdef CONFIG_PROVE_LOCKING */ #endif /* #ifdef CONFIG_PROVE_LOCKING */
static struct rtnl_link *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1]; 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) static inline int rtm_msgindex(int msgtype)
{ {
...@@ -272,10 +273,18 @@ EXPORT_SYMBOL_GPL(rtnl_unregister); ...@@ -272,10 +273,18 @@ EXPORT_SYMBOL_GPL(rtnl_unregister);
*/ */
void rtnl_unregister_all(int protocol) void rtnl_unregister_all(int protocol)
{ {
struct rtnl_link *handlers;
BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX); 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_msg_handlers[protocol] = NULL;
rtnl_unlock();
while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 0)
schedule();
kfree(handlers);
} }
EXPORT_SYMBOL_GPL(rtnl_unregister_all); EXPORT_SYMBOL_GPL(rtnl_unregister_all);
...@@ -4173,6 +4182,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, ...@@ -4173,6 +4182,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
if (dumpit == NULL) if (dumpit == NULL)
return -EOPNOTSUPP; return -EOPNOTSUPP;
refcount_inc(&rtnl_msg_handlers_ref[family]);
if (type == RTM_GETLINK) if (type == RTM_GETLINK)
min_dump_alloc = rtnl_calcit(skb, nlh); min_dump_alloc = rtnl_calcit(skb, nlh);
...@@ -4186,6 +4197,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *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); err = netlink_dump_start(rtnl, skb, nlh, &c);
} }
rtnl_lock(); rtnl_lock();
refcount_dec(&rtnl_msg_handlers_ref[family]);
return err; return err;
} }
......
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