[PATCH v4] Bluetooth: fix memory leak in error path of hci_alloc_dev()

[Bharath Reddy <kbreddy.rpbc@gmail.com>]

Early failures in Bluetooth HCI UART configuration leak SRCU percpu
memory.

When device initialization fails before hci_register_dev() completes,
the HCI_UNREGISTER flag is never set. As a result, when the device
reference count reaches zero, bt_host_release() evaluates this flag as
false and falls back to a direct kfree(hdev).

Because hci_release_dev() is bypassed, the SRCU struct initialized
early in hci_alloc_dev() is never cleaned up, resulting in a leak of
percpu memory.

Fix the leak by explicitly calling cleanup_srcu_struct() in the
fallback (unregistered) branch of bt_host_release() before freeing
the device.

Reported-by: syzbot+535ecc844591e50588a5@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=535ecc844591e50588a5
Tested-by: syzbot+535ecc844591e50588a5@syzkaller.appspotmail.com
Fixes: 1d6123102e9f ("Bluetooth: hci_core: Fix use-after-free in vhci_flush()")
Signed-off-by: Bharath Reddy <kbreddy.rpbc@gmail.com>
---
Changes in v4:
 - Include patch version history.

Changes in v3:
 - Added missing curly braces to the if/else block in bt_host_release() 
   to resolve a checkpatch.pl warning.
 - Added Fixes and Closes tags.

Changes in v2:
 - Fixed a NULL pointer dereference caused by v1. 
 - Moved cleanup_srcu_struct() to the fallback (unregistered) branch 
   of bt_host_release() instead of unconditionally calling hci_release_dev().

Changes in v1:
 - Initial patch (failed because it bypassed the HCI_UNREGISTER check).

 net/bluetooth/hci_sysfs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c
index 041ce9adc378..8957ce7c21b7 100644
--- a/net/bluetooth/hci_sysfs.c
+++ b/net/bluetooth/hci_sysfs.c
@@ -83,10 +83,12 @@ static void bt_host_release(struct device *dev)
 {
 	struct hci_dev *hdev = to_hci_dev(dev);
 
-	if (hci_dev_test_flag(hdev, HCI_UNREGISTER))
+	if (hci_dev_test_flag(hdev, HCI_UNREGISTER)) {
 		hci_release_dev(hdev);
-	else
+	} else {
+		cleanup_srcu_struct(&hdev->srcu);
 		kfree(hdev);
+	}
 	module_put(THIS_MODULE);
 }
 
-- 
2.34.1