From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikolay Aleksandrov Subject: [PATCH -net v2 1/2] netpoll: fix NULL pointer dereference in netpoll_cleanup Date: Thu, 19 Sep 2013 15:02:35 +0200 Message-ID: <1379595756-3527-2-git-send-email-nikolay@redhat.com> References: <1379595756-3527-1-git-send-email-nikolay@redhat.com> Cc: davem@davemloft.net To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:25516 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754001Ab3ISNGK (ORCPT ); Thu, 19 Sep 2013 09:06:10 -0400 In-Reply-To: <1379595756-3527-1-git-send-email-nikolay@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 --- v2: fix the style as requested net/core/netpoll.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 2c637e9..2ba363d 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); -- 1.8.1.4