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netpoll: fix NULL pointer dereference in netpoll_cleanup

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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>
This commit is contained in:
Nikolay Aleksandrov 2013-09-19 15:02:35 +02:00 committed by David S. Miller
parent c194992cbe
commit d0fe8c888b
1 changed files with 4 additions and 5 deletions
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9
net/core/netpoll.c
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@ -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);