| Message ID | 20150414110303.66edcfee@notabene.brown |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
Hello Neil, On Tue, Apr 14, 2015 at 11:03:03AM +1000, NeilBrown wrote: > On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb@suse.de> 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@vger.kernel.org (v4.0) > > Cc: Olivier Sobrie <olivier@sobrie.be> > > Signed-off-by: NeilBrown <neilb@suse.de> > > > > 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? Indeed, if I undestand correctly the code in tty_io.c, cleanup() method is also called when the open fails while kref_get is only done if the open succeeds. Sorry for that mess. I assume you get that crash when hso_start_serial_device() returns an error? At first sight, the patch below looks good to me. I'll test it in the next days. Thank you, Olivier > > Thanks, > NeilBrown > > From: NeilBrown <neil@brown.name> > 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@vger.kernel.org (v4.0) > Cc: Olivier Sobrie <olivier@sobrie.be> > Signed-off-by: NeilBrown <neil@brown.name> > > 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"); -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 14 Apr 2015 08:50:01 +0200 Olivier Sobrie <olivier@sobrie.be> wrote: > Hello Neil, > > On Tue, Apr 14, 2015 at 11:03:03AM +1000, NeilBrown wrote: > > On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb@suse.de> 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@vger.kernel.org (v4.0) > > > Cc: Olivier Sobrie <olivier@sobrie.be> > > > Signed-off-by: NeilBrown <neilb@suse.de> > > > > > > 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? > > Indeed, if I undestand correctly the code in tty_io.c, cleanup() method > is also called when the open fails while kref_get is only done if the > open succeeds. Sorry for that mess. > I assume you get that crash when hso_start_serial_device() returns > an error? Yes, that's correct. > > At first sight, the patch below looks good to me. > I'll test it in the next days. Thanks. NeilBrown > > Thank you, > > Olivier > > > > > Thanks, > > NeilBrown > > > > From: NeilBrown <neil@brown.name> > > 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@vger.kernel.org (v4.0) > > Cc: Olivier Sobrie <olivier@sobrie.be> > > Signed-off-by: NeilBrown <neil@brown.name> > > > > 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"); > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Tue, Apr 14, 2015 at 11:03:03AM +1000, NeilBrown wrote: > On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb@suse.de> 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@vger.kernel.org (v4.0) > > Cc: Olivier Sobrie <olivier@sobrie.be> > > Signed-off-by: NeilBrown <neilb@suse.de> > > > > 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? I tested the patch and it looks fine :-) Thank you, Olivier > > Thanks, > NeilBrown > > From: NeilBrown <neil@brown.name> > 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@vger.kernel.org (v4.0) > Cc: Olivier Sobrie <olivier@sobrie.be> Tested-by: Olivier Sobrie <olivier@sobrie.be> > Signed-off-by: NeilBrown <neil@brown.name> > > 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");
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");