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| author | Girish Moodalbail <girish.moodalbail@oracle.com> | 2017-10-27 09:00:16 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-10-28 12:17:21 +0200 |
| commit | dea6e19f4ef746aa18b4c33d1a7fed54356796ed (patch) | |
| tree | 812cc8b2a95206a026113b274c74d63bfadb1622 /drivers/net/macvtap.c | |
| parent | tcp: refresh tp timestamp before tcp_mtu_probe() (diff) | |
| download | linux-dea6e19f4ef746aa18b4c33d1a7fed54356796ed.tar.xz linux-dea6e19f4ef746aa18b4c33d1a7fed54356796ed.zip | |
tap: reference to KVA of an unloaded module causes kernel panic
The commit 9a393b5d5988 ("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: 9a393b5d5988ea4e (tap: tap as an independent module)
Signed-off-by: Girish Moodalbail <girish.moodalbail@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/macvtap.c')
| -rw-r--r-- | drivers/net/macvtap.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index c2d0ea2fb019..cba5cb3b849a 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -204,8 +204,8 @@ static int macvtap_init(void) { int err; - err = tap_create_cdev(&macvtap_cdev, &macvtap_major, "macvtap"); - + err = tap_create_cdev(&macvtap_cdev, &macvtap_major, "macvtap", + THIS_MODULE); if (err) goto out1; |