[PATCH 2/2] tuntap: fix leaking reference count

Jason Wang
2013-01-11T08:59:08Z

Reference count leaking of both module and sock were found:

- When a detached file were closed, its sock refcnt from device were not
released, solving this by add the sock_put().
- The module were hold or drop unconditionally in TUNSETPERSIST, which means we
if we set the persist flag for N times, we need unset it for another N
times. Solving this by only hold or drop an reference when there's a flag
change and also drop the reference count when the persist device is deleted.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/tun.c | 12 +++++++++---
1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9a46d70..d690dc8 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -429,8 +429,10 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
/* Drop read queue */
skb_queue_purge(&tfile->sk.sk_receive_queue);
tun_set_real_num_queues(tun);
- } else if (tfile->detached && clean)
+ } else if (tfile->detached && clean) {
tun = tun_enable_queue(tfile);
+ sock_put(&tfile->sk);
+ }

if (clean) {
if (tun && tun->numqueues == 0 && tun->numdisabled == 0 &&
@@ -481,6 +483,9 @@ static void tun_detach_all(struct net_device *dev)
sock_put(&tfile->sk);
}
BUG_ON(tun->numdisabled != 0);
+
+ if (tun->flags & TUN_PERSIST)
+ module_put(THIS_MODULE);
}

static int tun_attach(struct tun_struct *tun, struct file *file)
@@ -1881,10 +1886,11 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
/* Disable/Enable persist mode. Keep an extra reference to the
* module to prevent the module being unprobed.
*/
- if (arg) {
+ if (arg && !(tun->flags & TUN_PERSIST)) {
tun->flags |= TUN_PERSIST;
__module_get(THIS_MODULE);
- } else {
+ }
+ if (!arg && (tun->flags & TUN_PERSIST)) {
tun->flags &= ~TUN_PERSIST;
module_put(THIS_MODULE);
}
--
1.7.1