From d0fe8c888b1fd1a2f84b9962cabcb98a70988aec Mon Sep 17 00:00:00 2001 From: Nikolay Aleksandrov Date: Thu, 19 Sep 2013 15:02:35 +0200 Subject: netpoll: fix NULL pointer dereference in netpoll_cleanup I've been hitting a NULL ptr deref while using netconsole because the np->dev check and the pointer manipulation in netpoll_cleanup are done without rtnl and the following sequence happens when having a netconsole over a vlan and we remove the vlan while disabling the netconsole: CPU 1 CPU2 removes vlan and calls the notifier enters store_enabled(), calls netdev_cleanup which checks np->dev and then waits for rtnl executes the netconsole netdev release notifier making np->dev == NULL and releases rtnl continues to dereference a member of np->dev which at this point is == NULL Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- net/core/netpoll.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'net') diff --git a/net/core/netpoll.c b/net/core/netpoll.c index c3c7b27c112d..fc75c9e461b8 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -1284,15 +1284,14 @@ EXPORT_SYMBOL_GPL(__netpoll_free_async); void netpoll_cleanup(struct netpoll *np) { - if (!np->dev) - return; - rtnl_lock(); + if (!np->dev) + goto out; __netpoll_cleanup(np); - rtnl_unlock(); - dev_put(np->dev); np->dev = NULL; +out: + rtnl_unlock(); } EXPORT_SYMBOL(netpoll_cleanup); -- cgit v1.2.3