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Subject[ 07/48] netpoll: fix NULL pointer dereference in netpoll_cleanup
3.4-stable review patch.  If anyone has any objections, please let me know.


From: Nikolay Aleksandrov <>

[ 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:
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 <>
net/core/netpoll.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

--- 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;
+ if (!np->dev)
+ goto out;
- rtnl_unlock();
np->dev = NULL;
+ rtnl_unlock();

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