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authorDaniel Ritz2005-09-22 00:47:11 -0700
committerLinus Torvalds2005-09-22 07:58:24 -0700
commit4c898c7f2f286b204fefc5dddb568f755d195d0c (patch)
tree026fead9aef220a5fd994e2eaa269ed598651d39
parent0b50f81d5a63428f131ff20596f4e3d473e5b94f (diff)
[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 <pcmcia-modules> ;cardctl eject; rmmod <card driver, pcmcia modules>. 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 <daniel.ritz@gmx.ch> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--drivers/base/dd.c3
1 files changed, 3 insertions, 0 deletions
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);