Girish Moodalbail dea6e19f4e tap: reference to KVA of an unloaded module causes kernel panic ... The commit 9a393b5d59 ("tap: tap as an independent module") created a separate tap module that implements tap functionality and exports interfaces that will be used by macvtap and ipvtap modules to create create respective tap devices. However, that patch introduced a regression wherein the modules macvtap and ipvtap can be removed (through modprobe -r) while there are applications using the respective /dev/tapX devices. These applications cause kernel to hold reference to /dev/tapX through 'struct cdev macvtap_cdev' and 'struct cdev ipvtap_dev' defined in macvtap and ipvtap modules respectively. So, when the application is later closed the kernel panics because we are referencing KVA that is present in the unloaded modules. ----------8<------- Example ----------8<---------- $ sudo ip li add name mv0 link enp7s0 type macvtap $ sudo ip li show mv0 |grep mv0| awk -e '{print $1 $2}' 14:mv0@enp7s0: $ cat /dev/tap14 & $ lsmod |egrep -i 'tap|vlan' macvtap 16384 0 macvlan 24576 1 macvtap tap 24576 3 macvtap $ sudo modprobe -r macvtap $ fg cat /dev/tap14 ^C <...system panics...> BUG: unable to handle kernel paging request at ffffffffa038c500 IP: cdev_put+0xf/0x30 ----------8<-----------------8<---------- The fix is to set cdev.owner to the module that creates the tap device (either macvtap or ipvtap). With this set, the operations (in fs/char_dev.c) on char device holds and releases the module through cdev_get() and cdev_put() and will not allow the module to unload prematurely. Fixes: 9a393b5d59 (tap: tap as an independent module) Signed-off-by: Girish Moodalbail <girish.moodalbail@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2017-10-28 19:17:21 +09:00
..
ipvlan_core.c	ipvtap: IP-VLAN based tap driver	2017-02-11 20:59:41 -05:00
ipvlan_main.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next	2017-09-03 17:08:42 -07:00
ipvlan.h	net: add netlink_ext_ack argument to rtnl_link_ops.newlink	2017-06-26 23:13:21 -04:00
ipvtap.c	tap: reference to KVA of an unloaded module causes kernel panic	2017-10-28 19:17:21 +09:00
Makefile	ipvtap: IP-VLAN based tap driver	2017-02-11 20:59:41 -05:00