Patchwork [057/100] netpoll: fix NULL pointer dereference in netpoll_cleanup

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Submitter Luis Henriques
Date Oct. 11, 2013, 10:41 a.m.
Message ID <1381488130-30235-58-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/282670/
State New
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Luis Henriques - Oct. 11, 2013, 10:41 a.m.
3.5.7.23 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Aleksandrov <nikolay@redhat.com>

commit d0fe8c888b1fd1a2f84b9962cabcb98a70988aec upstream.

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 <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 net/core/netpoll.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

Patch

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index f9f40b9..5e81c49 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -920,15 +920,14 @@  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);