diff options
author | Girish Moodalbail <girish.moodalbail@oracle.com> | 2017-10-27 10:00:16 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-10-28 13:17:21 +0300 |
commit | dea6e19f4ef746aa18b4c33d1a7fed54356796ed (patch) | |
tree | 812cc8b2a95206a026113b274c74d63bfadb1622 /drivers/net | |
parent | ee1836aec4f5a977c1699a311db4d9027ef21ac8 (diff) | |
download | linux-dea6e19f4ef746aa18b4c33d1a7fed54356796ed.tar.xz |
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')
-rw-r--r-- | drivers/net/ipvlan/ipvtap.c | 4 | ||||
-rw-r--r-- | drivers/net/macvtap.c | 4 | ||||
-rw-r--r-- | drivers/net/tap.c | 5 |
3 files changed, 7 insertions, 6 deletions
diff --git a/drivers/net/ipvlan/ipvtap.c b/drivers/net/ipvlan/ipvtap.c index 5dea2063dbc8..0bcc07f346c3 100644 --- a/drivers/net/ipvlan/ipvtap.c +++ b/drivers/net/ipvlan/ipvtap.c @@ -197,8 +197,8 @@ static int ipvtap_init(void) { int err; - err = tap_create_cdev(&ipvtap_cdev, &ipvtap_major, "ipvtap"); - + err = tap_create_cdev(&ipvtap_cdev, &ipvtap_major, "ipvtap", + THIS_MODULE); if (err) goto out1; 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; diff --git a/drivers/net/tap.c b/drivers/net/tap.c index 98ee6cc2875d..1b10fcc6a58d 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -1249,8 +1249,8 @@ static int tap_list_add(dev_t major, const char *device_name) return 0; } -int tap_create_cdev(struct cdev *tap_cdev, - dev_t *tap_major, const char *device_name) +int tap_create_cdev(struct cdev *tap_cdev, dev_t *tap_major, + const char *device_name, struct module *module) { int err; @@ -1259,6 +1259,7 @@ int tap_create_cdev(struct cdev *tap_cdev, goto out1; cdev_init(tap_cdev, &tap_fops); + tap_cdev->owner = module; err = cdev_add(tap_cdev, *tap_major, TAP_NUM_DEVS); if (err) goto out2; |