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Commit d0fe8c88 authored by Nikolay Aleksandrov's avatar Nikolay Aleksandrov Committed by David S. Miller
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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: default avatarNikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c194992c

net/core/netpoll.c

+4 −5
Original line number Original line Diff line number Diff line
@@ -1284,15 +1284,14 @@ EXPORT_SYMBOL_GPL(__netpoll_free_async); 




void netpoll_cleanup(struct netpoll *np)

void netpoll_cleanup(struct netpoll *np)

{

{

	if (!np->dev)

		return;



	rtnl_lock();

	rtnl_lock();

	if (!np->dev)

		goto out;

	__netpoll_cleanup(np);

	__netpoll_cleanup(np);

	rtnl_unlock();



	dev_put(np->dev);

	dev_put(np->dev);

	np->dev = NULL;

	np->dev = NULL;

out:

	rtnl_unlock();

}

}

EXPORT_SYMBOL(netpoll_cleanup);

EXPORT_SYMBOL(netpoll_cleanup);