netpoll: fix NULL pointer dereference in netpoll_cleanup
authorNikolay Aleksandrov <nikolay@redhat.com>
Thu, 19 Sep 2013 13:02:35 +0000 (15:02 +0200)
committerDavid S. Miller <davem@davemloft.net>
Thu, 19 Sep 2013 18:15:53 +0000 (14:15 -0400)
commitd0fe8c888b1fd1a2f84b9962cabcb98a70988aec
tree0d148e7dfea45c04842617aa32c9be50235d606a
parentc194992cbe71c20bb3623a566af8d11b0bfaa721
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: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/core/netpoll.c