[PATCH] Bluetooth: hci_sync: Serialize local codec list cleanup

[PATCH] Bluetooth: hci_sync: Serialize local codec list cleanup

[Chengfeng Ye]

hci_dev_close_sync() clears hdev->local_codecs after releasing hdev->lock.
Codec list additions and both traversals in sco_sock_getsockopt() use that
lock, but the close path does not. A close and BT_CODEC query can therefore
interleave as follows:

  hci_dev_close_sync()          sco_sock_getsockopt()
                                hci_dev_lock()
                                fetch codec entry
  hci_codec_list_clear()
    kfree(entry)
                                read entry->id

The reader then accesses an entry which the close path has freed. KASAN
reported:

  BUG: KASAN: slab-use-after-free in sco_sock_getsockopt+0xfa0/0xfe0
  Read of size 1 at addr ffff8881001c3450
  Call Trace:
   sco_sock_getsockopt+0xfa0/0xfe0
   do_sock_getsockopt+0x537/0x7b0
   __sys_getsockopt+0xf2/0x170
  Allocated by task 92:
   hci_codec_list_add.isra.0+0x2c/0x440
   hci_read_codec_capabilities+0x224/0x590
   hci_read_supported_codecs+0x2c2/0x640
  Freed by task 92:
   kfree+0x131/0x3c0
   hci_codec_list_clear+0xd8/0x160
   hci_dev_close_sync+0x92a/0xfa0

Take hdev->lock around the clear operation at its existing point in the
close path. This makes the clear wait for active readers and prevents a new
traversal until the list is empty without changing teardown ordering.

Fixes: b938790e7054 ("Bluetooth: hci_codec: Fix leaking content of local_codecs")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
---
 net/bluetooth/hci_sync.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index b5897545d795..da748e14e5f3 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -5648,7 +5648,9 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 	memset(hdev->eir, 0, sizeof(hdev->eir));
 	memset(hdev->dev_class, 0, sizeof(hdev->dev_class));
 	bacpy(&hdev->random_addr, BDADDR_ANY);
+	hci_dev_lock(hdev);
 	hci_codec_list_clear(&hdev->local_codecs);
+	hci_dev_unlock(hdev);
 
 	hci_dev_put(hdev);
 	return err;
-- 
2.43.0