From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 27 Jul 2021 06:12:04 +0900
Subject: Bluetooth: defer cleanup of resources in hci_unregister_dev()
Patch-mainline: v5.15-rc1
Git-commit: 58ce6d5b271ab25fb2056f84a8e5546945eb5fc9
References: jsc#PED-1407

syzbot is hitting might_sleep() warning at hci_sock_dev_event()
due to calling lock_sock() with rw spinlock held [1].

It seems that history of this locking problem is a trial and error.

Commit b40df5743ee8aed8 ("[PATCH] bluetooth: fix socket locking in
hci_sock_dev_event()") in 2.6.21-rc4 changed bh_lock_sock() to lock_sock()
as an attempt to fix lockdep warning.

Then, commit 4ce61d1c7a8ef4c1 ("[BLUETOOTH]: Fix locking in
hci_sock_dev_event().") in 2.6.22-rc2 changed lock_sock() to
local_bh_disable() + bh_lock_sock_nested() as an attempt to fix
sleep in atomic context warning.

Then, commit 4b5dd696f81b210c ("Bluetooth: Remove local_bh_disable() from
hci_sock.c") in 3.3-rc1 removed local_bh_disable().

Then, commit e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF
of hdev object") in 5.13-rc5 again changed bh_lock_sock_nested() to
lock_sock() as an attempt to fix CVE-2021-3573.

This difficulty comes from current implementation that
hci_sock_dev_event(HCI_DEV_UNREG) is responsible for dropping all
references from sockets because hci_unregister_dev() immediately reclaims
resources as soon as returning from hci_sock_dev_event(HCI_DEV_UNREG).
But the history suggests that hci_sock_dev_event(HCI_DEV_UNREG) was not
doing what it should do.

Therefore, instead of trying to detach sockets from device, let's accept
not detaching sockets from device at hci_sock_dev_event(HCI_DEV_UNREG),
by moving actual cleanup of resources from hci_unregister_dev() to
hci_release_dev() which is called by bt_host_release when all references
to this unregistered device (which is a kobject) are gone.

Joey Lee:
This patch has modified to sync the final code with v5.15 mainline.
The original 58ce6d5b271 patch conflicts with e04480920d1 in v5.14
in mainline. 

Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1]
Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Fixes: e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 include/net/bluetooth/hci_core.h |    2 +-
 net/bluetooth/hci_core.c         |    8 +++++---
 net/bluetooth/hci_sysfs.c        |    3 +--
 3 files changed, 7 insertions(+), 6 deletions(-)

--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1230,7 +1230,7 @@ struct hci_dev *hci_alloc_dev(void);
 void hci_free_dev(struct hci_dev *hdev);
 int hci_register_dev(struct hci_dev *hdev);
 void hci_unregister_dev(struct hci_dev *hdev);
-void hci_cleanup_dev(struct hci_dev *hdev);
+void hci_release_dev(struct hci_dev *hdev);
 int hci_suspend_dev(struct hci_dev *hdev);
 int hci_resume_dev(struct hci_dev *hdev);
 int hci_reset_dev(struct hci_dev *hdev);
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4034,13 +4034,13 @@ void hci_unregister_dev(struct hci_dev *
 	}
 
 	device_del(&hdev->dev);
-	/* Actual cleanup is deferred until hci_cleanup_dev(). */
+	/* Actual cleanup is deferred until hci_release_dev(). */
 	hci_dev_put(hdev);
 }
 EXPORT_SYMBOL(hci_unregister_dev);
 
-/* Cleanup HCI device */
-void hci_cleanup_dev(struct hci_dev *hdev)
+/* Release HCI device */
+void hci_release_dev(struct hci_dev *hdev)
 {
 	debugfs_remove_recursive(hdev->debugfs);
 	kfree_const(hdev->hw_info);
@@ -4067,7 +4067,9 @@ void hci_cleanup_dev(struct hci_dev *hde
 	hci_dev_unlock(hdev);
 
 	ida_simple_remove(&hci_index_ida, hdev->id);
+	kfree(hdev);
 }
+EXPORT_SYMBOL(hci_release_dev);
 
 /* Suspend HCI device */
 int hci_suspend_dev(struct hci_dev *hdev)
--- a/net/bluetooth/hci_sysfs.c
+++ b/net/bluetooth/hci_sysfs.c
@@ -85,8 +85,7 @@ static void bt_host_release(struct devic
 	struct hci_dev *hdev = to_hci_dev(dev);
 
 	if (hci_dev_test_flag(hdev, HCI_UNREGISTER))
-		hci_cleanup_dev(hdev);
-	kfree(hdev);
+		hci_release_dev(hdev);
 	module_put(THIS_MODULE);
 }