[PATCH 6.6.y 1/2] driver core: Check drivers_autoprobe for all added devices

[Sasha Levin <sashal@kernel.org>]

From: Vincent Liu <vincent.liu@nutanix.com>

[ Upstream commit ea34511aaf755349999a1067b2984a541bee1492 ]

When a device is hot-plugged, the drivers_autoprobe sysfs attribute is
not checked (at least for PCI devices). This means that
drivers_autoprobe is not working as intended, e.g. hot-plugged PCI
devices will still be autoprobed and bound to drivers even with
drivers_autoprobe disabled.

The problem likely started when device_add() was removed from
pci_bus_add_device() in commit 4f535093cf8f ("PCI: Put pci_dev in device
tree as early as possible") which means that the check for
drivers_autoprobe which used to happen in bus_probe_device() is no
longer present (previously bus_add_device() calls bus_probe_device()).
Conveniently, in commit 91703041697c ("PCI: Allow built-in drivers to
use async initial probing") device_attach() was replaced with
device_initial_probe() which faciliates this change to push the check
for drivers_autoprobe into device_initial_probe().

Make sure all devices check drivers_autoprobe by pushing the
drivers_autoprobe check into device_initial_probe(). This will only
affect devices on the PCI bus for now as device_initial_probe() is only
called by pci_bus_add_device() and bus_probe_device(), but
bus_probe_device() already checks for autoprobe, so callers of
bus_probe_device() should not observe changes on autoprobing.
Note also that pushing this check into device_initial_probe() rather
than device_attach() makes it only affect automatic probing of
drivers (e.g. when a device is hot-plugged), userspace can still choose
to manually bind a driver by writing to drivers_probe sysfs attribute,
even with autoprobe disabled.

Any future callers of device_initial_probe() will respect the
drivers_autoprobe sysfs attribute, which is the intended purpose of
drivers_autoprobe.

Signed-off-by: Vincent Liu <vincent.liu@nutanix.com>
Link: https://patch.msgid.link/20251022120740.2476482-1-vincent.liu@nutanix.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Apply the bus-side change to the existing shared probe helper, preserving
the deferred-probe parent locking. PCI still calls device_attach(), so
its probe behaviour is unchanged. Retain this change to prepare
device_initial_probe() for the async-attach retry handling.

Stable-dep-of: 187a62f99da2 ("driver core: take parent lock in async device attach")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/base/bus.c |  3 +--
 drivers/base/dd.c  | 10 +++++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 65c138dc9b3fb..dccfbc5f389bb 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -570,8 +570,7 @@ static void __bus_probe_device(struct device *dev)
 	if (!sp)
 		return;
 
-	if (sp->drivers_autoprobe)
-		device_initial_probe(dev);
+	device_initial_probe(dev);
 
 	mutex_lock(&sp->mutex);
 	list_for_each_entry(sif, &sp->interfaces, node)
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index c6ba7402bd514..4accc885a9d44 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -1156,7 +1156,15 @@ EXPORT_SYMBOL_GPL(device_attach);
 
 void device_initial_probe(struct device *dev)
 {
-	__device_attach(dev, true);
+	struct subsys_private *sp = bus_to_subsys(dev->bus);
+
+	if (!sp)
+		return;
+
+	if (sp->drivers_autoprobe)
+		__device_attach(dev, true);
+
+	subsys_put(sp);
 }
 
 /*
-- 
2.53.0