On Wed, Sep 25, 2013 at 5:39 AM, Benson Leung <bleung@xxxxxxxxxxxx> wrote: > The put_device(dev) at the bottom of the loop of device_shutdown > may result in the dev being cleaned up. In device_create_release, > the dev is kfreed. > > However, device_shutdown attempts to use the dev pointer again after > put_device by referring to dev->parent. > > Copy the parent pointer instead to avoid this condition. Right. > > This bug was found on Chromium OS's chromeos-3.8, which is based on v3.8.11. > See bug report : https://code.google.com/p/chromium/issues/detail?id=297842 > This can easily be reproduced when shutting down with > hidraw devices that report battery condition. > Two examples are the HP Bluetooth Mouse X4000b and the Apple Magic Mouse. > For example, with the magic mouse : > The dev in question is "hidraw0" > dev->parent is "magicmouse" > > In the course of the shutdown for this device, the input event cleanup calls > a put on hidraw0, decrementing its reference count. > When we finally get to put_device(dev) in device_shutdown, kobject_cleanup > is called and device_create_release does kfree(dev). > dev->parent is no longer valid, and we may crash in > put_device(dev->parent). > > This change should be applied on any kernel with this change : > d1c6c030fcec6f860d9bb6c632a3ebe62e28440b > > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Benson Leung <bleung@xxxxxxxxxxxx> > --- > drivers/base/core.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index c7cfadc..34bd546 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -2026,6 +2026,8 @@ void device_shutdown(void) > * devices offline, even as the system is shutting down. > */ > while (!list_empty(&devices_kset->list)) { > + struct device *parent; > + > dev = list_entry(devices_kset->list.prev, struct device, > kobj.entry); > > @@ -2034,7 +2036,8 @@ void device_shutdown(void) > * prevent it from being freed because parent's > * lock is to be held > */ > - get_device(dev->parent); > + parent = dev->parent; > + get_device(parent); It is better to save one line by below: parent = get_device(dev->parent); > get_device(dev); > /* > * Make sure the device is off the kset list, in the > @@ -2044,8 +2047,8 @@ void device_shutdown(void) > spin_unlock(&devices_kset->list_lock); > > /* hold lock to avoid race with probe/release */ > - if (dev->parent) > - device_lock(dev->parent); > + if (parent) > + device_lock(parent); > device_lock(dev); > > /* Don't allow any more runtime suspends */ > @@ -2063,11 +2066,11 @@ void device_shutdown(void) > } > > device_unlock(dev); > - if (dev->parent) > - device_unlock(dev->parent); > + if (parent) > + device_unlock(parent); > > put_device(dev); > - put_device(dev->parent); > + put_device(parent); > > spin_lock(&devices_kset->list_lock); > } Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html