[PATCH] Bluetooth: hci_event: fix LE list UAF on reset

[Chengfeng Ye]

hci_cc_reset() clears the LE accept and resolving lists without taking
hdev->lock. Other command-complete handlers serialize updates to these
lists with that lock, and the debugfs readers hold it while walking them.

This permits the reset completion and a debugfs read to interleave as
follows:

  hci_rx_work                 debugfs reader
  -----------                 --------------
                              lock hdev->lock
                              fetch current entry
  list_del(entry)
  kfree(entry)
                              read entry fields

The reader then dereferences a freed list entry and may follow its stale
next pointer.

KASAN reported:

  BUG: KASAN: slab-use-after-free in white_list_show+0x15f/0x180
  Read of size 1 at addr ffff8881015dab16 by task poc/95

  Call Trace:
   white_list_show+0x15f/0x180
   seq_read_iter+0x3ff/0x1190
   seq_read+0x267/0x3d0
   vfs_read+0x177/0xa20
   ksys_read+0xf7/0x1c0

  Allocated by task 91:
   hci_bdaddr_list_add+0x1a6/0x3a0
   hci_cc_le_add_to_accept_list+0xab/0x140
   hci_cmd_complete_evt+0x26c/0x9a0
   hci_event_packet+0x454/0xb20
   hci_rx_work+0x293/0x730

  Freed by task 90:
   kfree+0x131/0x3c0
   hci_bdaddr_list_clear+0xd8/0x160
   hci_cc_reset+0x28a/0x370
   hci_cmd_complete_evt+0x26c/0x9a0
   hci_event_packet+0x454/0xb20
   hci_rx_work+0x293/0x730

Take hdev->lock around both list clears. This matches the existing
mutation and traversal locking convention.

Fixes: a4d5504d5c39 ("Bluetooth: Clear LE white list when resetting controller")
Fixes: cfdb0c2d095a ("Bluetooth: Store Resolv list size")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Chengfeng Ye <nicoyip.dev@xxxxxxxxx>
---
 net/bluetooth/hci_event.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 741d658e9630..00e2683f99ed 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -294,8 +294,10 @@ static u8 hci_cc_reset(struct hci_dev *hdev, void *data, struct sk_buff *skb)
 
 	hdev->ssp_debug_mode = 0;
 
+	hci_dev_lock(hdev);
 	hci_bdaddr_list_clear(&hdev->le_accept_list);
 	hci_bdaddr_list_clear(&hdev->le_resolv_list);
+	hci_dev_unlock(hdev);
 
 	return rp->status;
 }
-- 
2.43.0