netpoll: fix NULL pointer dereference in netpoll_cleanup
authorNikolay Aleksandrov <nikolay@redhat.com>
Thu, 19 Sep 2013 13:02:35 +0000 (15:02 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 13 Oct 2013 23:08:29 +0000 (16:08 -0700)
commite66bdd7106911886aebf118e1c1aebb5a26d0752
tree98a8771d5ba1c96c98375620c72299639e9e042b
parent0885f6b8bb0403a56546d302e749c1defe47339d
netpoll: fix NULL pointer dereference in netpoll_cleanup

[ 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:
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/core/netpoll.c