From: Nikolay Aleksandrov Date: Thu, 19 Sep 2013 13:02:35 +0000 (+0200) Subject: netpoll: fix NULL pointer dereference in netpoll_cleanup X-Git-Tag: v3.0.100~33 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f6f88d6f41938e39971a5c0fce3aa8d26d3dd9de;p=thirdparty%2Fkernel%2Fstable.git netpoll: fix NULL pointer dereference in netpoll_cleanup [ Upstream commit d0fe8c888b1fd1a2f84b9962cabcb98a70988aec ] 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 207a178f73b25..c4971372340ad 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -927,15 +927,14 @@ EXPORT_SYMBOL_GPL(__netpoll_cleanup); 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);