Trying to register a device on a bus which has not yet been registered
used to trigger a NULL-pointer dereference, but since the const bus
structure rework registration instead succeeds without the device being
added to the bus.

This specifically means that the device will never bind to a driver and
that the bus sysfs attributes are not created (i.e. as if the device had
no bus).

Reject devices with unregistered buses to catch any callers that get
the ordering wrong and to handle bus registration failures more
gracefully.

Fixes: 5221b82d46f2 ("driver core: bus: bus_add/probe/remove_device() cleanups")
Cc: stable@vger.kernel.org	# 6.3
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---

Changes in v2:
 - amend commit message with implications of the device not being added
   to the bus


 drivers/base/bus.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 8b6722ff8590..d17bd91490ee 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -544,10 +544,10 @@ static const struct attribute_group driver_override_dev_group = {
  */
 int bus_add_device(struct device *dev)
 {
-	struct subsys_private *sp = bus_to_subsys(dev->bus);
+	struct subsys_private *sp;
 	int error;
 
-	if (!sp) {
+	if (!dev->bus) {
 		/*
 		 * This is a normal operation for many devices that do not
 		 * have a bus assigned to them, just say that all went
@@ -556,6 +556,13 @@ int bus_add_device(struct device *dev)
 		return 0;
 	}
 
+	sp = bus_to_subsys(dev->bus);
+	if (!sp) {
+		pr_err("%s: cannot add device '%s' to unregistered bus '%s'\n",
+		       __func__, dev_name(dev), dev->bus->name);
+		return -EINVAL;
+	}
+
 	/*
 	 * Reference in sp is now incremented and will be dropped when
 	 * the device is removed from the bus
-- 
2.53.0

On Thu, 30 Apr 2026 11:17:18 +0200, Johan Hovold wrote:
> [PATCH v2] driver core: reject devices with unregistered buses

Applied, thanks!

  Branch: driver-core-testing
  Tree:   git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git

[1/1] driver core: reject devices with unregistered buses
      commit: 13c7c1752b6c

The patch will appear in the next linux-next integration (typically within 24
hours on weekdays).

The patch is in the driver-core-testing branch and will be promoted to
driver-core-next after validation.