On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb@xxxxxxx> wrote: > > > Prior to > commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b > hso: fix crash when device disappears while serial port is open > > hso_serial_open would always kref_get(&serial->parent->ref) before > returning zero. > Since that commit, it only calls kref_get when returning 0 if > serial->port.count was zero. > > This results in calls to > kref_put(&serial->parent->ref, hso_serial_ref_free); > > after hso_serial_ref_free has been called, which dereferences a freed > pointer. > > This patch adds the missing kref_get(). > > Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b > Cc: stable@xxxxxxxxxxxxxxx (v4.0) > Cc: Olivier Sobrie <olivier@xxxxxxxxx> > Signed-off-by: NeilBrown <neilb@xxxxxxx> > > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c > index 75befc1bd816..6848fc903340 100644 > --- a/drivers/net/usb/hso.c > +++ b/drivers/net/usb/hso.c > @@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) > } > } else { > D1("Port was already open"); > + kref_get(&serial->parent->ref); > } > > usb_autopm_put_interface(serial->parent->interface); Sorry - that was wrong. I'm getting crashes which strongly suggest the kref_put is being called extra times, but I misunderstood the code and was hasty. Maybe this instead? Thanks, NeilBrown From: NeilBrown <neil@xxxxxxxxxx> Date: Tue, 14 Apr 2015 09:33:03 +1000 Subject: [PATCH] hso: fix refcnt leak in recent patch. Prior to commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b hso: fix crash when device disappears while serial port is open a kref_get on serial->parent->ref would be taken on each open, and it would be kref_put on each close. Now the kref_put happens when the tty_struct is finally put (via the 'cleanup') providing tty->driver_data has been set. So the kref_get must be called exact once when tty->driver_data is set. With the current code, if the first open fails the kref_get() is never called, but the kref_put() is called, leaving to a crash. So change the kref_get call to happen exactly when ->driver_data is changed from NULL to non-NULL. Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b Cc: stable@xxxxxxxxxxxxxxx (v4.0) Cc: Olivier Sobrie <olivier@xxxxxxxxx> Signed-off-by: NeilBrown <neil@xxxxxxxxxx> diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c index 75befc1bd816..17fd3820263a 100644 --- a/drivers/net/usb/hso.c +++ b/drivers/net/usb/hso.c @@ -1278,6 +1278,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) D1("Opening %d", serial->minor); /* setup */ + if (tty->driver_data == NULL) + kref_get(&serial->parent->ref); tty->driver_data = serial; tty_port_tty_set(&serial->port, tty); @@ -1294,8 +1296,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) if (result) { hso_stop_serial_device(serial->parent); serial->port.count--; - } else { - kref_get(&serial->parent->ref); } } else { D1("Port was already open");
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