From 4c898c7f2f286b204fefc5dddb568f755d195d0c Mon Sep 17 00:00:00 2001 From: Daniel Ritz Date: Thu, 22 Sep 2005 00:47:11 -0700 Subject: [PATCH] [PATCH] Driver Core: fis bus rescan devices race bus_rescan_devices_helper() does not hold the dev->sem when it checks for !dev->driver(). device_attach() holds the sem, but calls again device_bind_driver() even when dev->driver is set. What happens is that a first device_attach() call (module insertion time) is on the way binding the device to a driver. Another thread calls bus_rescan_devices(). Now when bus_rescan_devices_helper() checks for dev->driver it is still NULL 'cos the the prior device_attach() is not yet finished. But as soon as the first one releases the dev->sem the second device_attach() tries to rebind the already bound device again. device_bind_driver() does this blindly which leads to a corrupt driver->klist_devices list (the device links itself, the head points to the device). Later a call to device_release_driver() sets dev->driver to NULL and breaks the link it has to itself on knode_driver. Rmmoding the driver later calls driver_detach() which leads to an endless loop 'cos the list head in klist_devices still points to the device. And since dev->driver is NULL it's stuck with the same device forever. Boom. And rmmod hangs. Very easy to reproduce with new-style pcmcia and a 16bit card. Just loop modprobe ;cardctl eject; rmmod . Easiest fix is to check if the device is already bound to a driver in device_bind_driver(). This avoids the double binding. Signed-off-by: Daniel Ritz Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman Signed-off-by: Linus Torvalds --- drivers/base/dd.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index d5bbce38282f..3565e9795301 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -40,6 +40,9 @@ */ void device_bind_driver(struct device * dev) { + if (klist_node_attached(&dev->knode_driver)) + return; + pr_debug("bound device '%s' to driver '%s'\n", dev->bus_id, dev->driver->name); klist_add_tail(&dev->knode_driver, &dev->driver->klist_devices); -- 2.20.1