[PATCH v2 1/2] driver core: faux: fix root device registration

Johan Hovold
2026-04-24T15:32:15Z

A recent change made the faux bus root device be allocated dynamically
but failed to provide a release function to free the memory when the
last reference is dropped (on theoretical failure to register the device
or bus).

Fix this by using root_device_register() instead of open coding.

Also add the missing sanity check when registering faux devices to avoid
use-after-free if the bus failed to register (which would previously
have triggered a bunch of use-after-free warnings).

Fixes: 61b76d07d2b4 ("driver core: faux: stop using static struct device")
Cc: stable@vger.kernel.org # 7.0
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/base/faux.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/base/faux.c b/drivers/base/faux.c
index fb3e42f21362..3d1d1eafb473 100644
--- a/drivers/base/faux.c
+++ b/drivers/base/faux.c
@@ -133,6 +133,9 @@ struct faux_device *faux_device_create_with_groups(const char *name,
struct device *dev;
int ret;

+ if (!faux_bus_root)
+ return NULL;
+
faux_obj = kzalloc_obj(*faux_obj);
if (!faux_obj)
return NULL;
@@ -232,19 +235,12 @@ EXPORT_SYMBOL_GPL(faux_device_destroy);

int __init faux_bus_init(void)
{
+ struct device *root;
int ret;

- faux_bus_root = kzalloc_obj(*faux_bus_root);
- if (!faux_bus_root)
- return -ENOMEM;
-
- dev_set_name(faux_bus_root, "faux");
-
- ret = device_register(faux_bus_root);
- if (ret) {
- put_device(faux_bus_root);
- return ret;
- }
+ root = root_device_register("faux");
+ if (IS_ERR(root))
+ return PTR_ERR(root);

ret = bus_register(&faux_bus_type);
if (ret)
@@ -254,12 +250,14 @@ int __init faux_bus_init(void)
if (ret)
goto error_driver;

+ faux_bus_root = root;
+
return ret;

error_driver:
bus_unregister(&faux_bus_type);

error_bus:
- device_unregister(faux_bus_root);
+ root_device_unregister(root);
return ret;
}
--
2.53.0