From c71380ff0b199f1e8be5ca46dd91262f7fbe4cb4 Mon Sep 17 00:00:00 2001 From: Nikolay Aleksandrov Date: Thu, 19 Sep 2013 15:02:36 +0200 Subject: [PATCH] netconsole: fix a deadlock with rtnl and netconsole's mutex This bug was introduced by commit 7a163bfb7ce50895bbe67300ea610d31b9c09230 ("netconsole: avoid a crash with multiple sysfs writers"). In store_enabled() we have the following sequence: acquire nt->mutex then rtnl, but in the netconsole netdev notifier we have rtnl then nt->mutex effectively leading to a deadlock. The NULL pointer dereference that the above commit tries to fix is actually due to another bug in netpoll_cleanup(). This is fixed by dropping the mutex from the netdev notifier as it's already protected by rtnl. Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- drivers/net/netconsole.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index dcb21347c670..adeee615dd19 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -684,15 +684,12 @@ restart: case NETDEV_RELEASE: case NETDEV_JOIN: case NETDEV_UNREGISTER: - /* - * rtnl_lock already held + /* rtnl_lock already held * we might sleep in __netpoll_cleanup() */ spin_unlock_irqrestore(&target_list_lock, flags); - mutex_lock(&nt->mutex); __netpoll_cleanup(&nt->np); - mutex_unlock(&nt->mutex); spin_lock_irqsave(&target_list_lock, flags); dev_put(nt->np.dev);