Commit 4fa3e78b authored Jan 29, 2013 by Bjorn Helgaas Committed by Greg Kroah-Hartman Feb 03, 2013

Driver core: treat unregistered bus_types as having no devices

A bus_type has a list of devices (klist_devices), but the list and the
subsys_private structure that contains it are not initialized until the
bus_type is registered with bus_register().

The panic/reboot path has fixups that look up devices in pci_bus_type.  If
we panic before registering pci_bus_type, the bus_type exists but the list
does not, so mach_reboot_fixups() trips over a null pointer and panics
again:

    mach_reboot_fixups
      pci_get_device
        ..
          bus_find_device(&pci_bus_type, ...)
            bus->p is NULL

Joonsoo reported a problem when panicking before PCI was initialized.
I think this patch should be sufficient to replace the patch he posted
here: https://lkml.org/lkml/2012/12/28/75

 ("[PATCH] x86, reboot: skip
reboot_fixups in early boot phase")

Reported-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 422d26b6

drivers/base/bus.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -290,7 +290,7 @@ int bus_for_each_dev(struct bus_type bus, struct device start,
	struct device *dev;		struct device *dev;
	int error = 0;		int error = 0;

	if (!bus)		if (!bus \|\| !bus->p)
	return -EINVAL;		return -EINVAL;

	klist_iter_init_node(&bus->p->klist_devices, &i,		klist_iter_init_node(&bus->p->klist_devices, &i,
	@@ -324,7 +324,7 @@ struct device bus_find_device(struct bus_type bus,
	struct klist_iter i;		struct klist_iter i;
	struct device *dev;		struct device *dev;

	if (!bus)		if (!bus \|\| !bus->p)
	return NULL;		return NULL;

	klist_iter_init_node(&bus->p->klist_devices, &i,		klist_iter_init_node(&bus->p->klist_devices, &i,