[PATCH] Bluetooth: hci_sync: Fix inquiry cache use-after-free

[Chengfeng Ye]

The sync command worker holds hdev->req_lock, but inquiry-cache updates
and flushes use hdev->lock. Both hci_acl_create_conn_sync() and
hci_stop_discovery_sync() look up entries and read their fields without
taking hdev->lock.

After either lookup returns, a concurrent HCIINQUIRY ioctl can acquire
hdev->lock and flush the cache, freeing the entry. The worker then reads
the freed entry while preparing a create-connection or remote-name-cancel
command. The list traversal also races with cache updates and removal.

KASAN reported these accesses:

  BUG: KASAN: slab-use-after-free in hci_acl_create_conn_sync+0x5f1/0x650
  Workqueue: hci0 hci_cmd_sync_work
  Call Trace:
   hci_acl_create_conn_sync+0x5f1/0x650
   hci_cmd_sync_work+0x13c/0x290

  Allocated by task 90:
   hci_inquiry_cache_update+0x3e6/0x7d0
   hci_inquiry_result_evt+0x3cb/0x560

  Freed by task 93:
   hci_inquiry_cache_flush+0x111/0x2b0
   hci_inquiry+0x2f2/0x780
   hci_sock_ioctl+0x269/0x5f0

  BUG: KASAN: slab-use-after-free in hci_stop_discovery_sync+0x3b1/0x3c0
  Workqueue: hci0 hci_cmd_sync_work
  Call Trace:
   hci_stop_discovery_sync+0x3b1/0x3c0
   hci_cmd_sync_work+0x173/0x300

  Allocated by task 86:
   hci_inquiry_cache_update+0x483/0x940
   hci_inquiry_result_evt+0x3cb/0x560

  Freed by task 91:
   hci_inquiry_cache_flush+0x13e/0x2f0
   hci_inquiry+0x2f2/0x780
   hci_sock_ioctl+0x269/0x5f0

Hold hdev->lock across each lookup and all reads from its result. Copy the
remote address before unlocking so discovery cancellation does not retain
a cache entry pointer. Release the lock before sending synchronous HCI
commands, since their completion handlers may need the same lock.

Fixes: cf75ad8b41d2 ("Bluetooth: hci_sync: Convert MGMT_SET_POWERED")
Fixes: 45340097ce6e ("Bluetooth: hci_conn: Only do ACL connections sequentially")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Chengfeng Ye <nicoyip.dev@xxxxxxxxx>
---
 net/bluetooth/hci_sync.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 74e2b04c84b2..0712ed09edd5 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -5764,6 +5764,7 @@ int hci_stop_discovery_sync(struct hci_dev *hdev)
 {
 	struct discovery_state *d = &hdev->discovery;
 	struct inquiry_entry *e;
+	bdaddr_t addr;
 	int err;
 
 	bt_dev_dbg(hdev, "state %u", hdev->discovery.state);
@@ -5799,15 +5800,21 @@ int hci_stop_discovery_sync(struct hci_dev *hdev)
 		return 0;
 
 	if (d->state == DISCOVERY_RESOLVING || d->state == DISCOVERY_STOPPING) {
+		hci_dev_lock(hdev);
 		e = hci_inquiry_cache_lookup_resolve(hdev, BDADDR_ANY,
 						     NAME_PENDING);
-		if (!e)
+		if (!e) {
+			hci_dev_unlock(hdev);
 			return 0;
+		}
+
+		bacpy(&addr, &e->data.bdaddr);
+		hci_dev_unlock(hdev);
 
 		/* Ignore cancel errors since it should interfere with stopping
 		 * of the discovery.
 		 */
-		hci_remote_name_cancel_sync(hdev, &e->data.bdaddr);
+		hci_remote_name_cancel_sync(hdev, &addr);
 	}
 
 	return 0;
@@ -7236,6 +7243,7 @@ static int hci_acl_create_conn_sync(struct hci_dev *hdev, void *data)
 	bacpy(&cp.bdaddr, &conn->dst);
 	cp.pscan_rep_mode = 0x02;
 
+	hci_dev_lock(hdev);
 	ie = hci_inquiry_cache_lookup(hdev, &conn->dst);
 	if (ie) {
 		if (inquiry_entry_age(ie) <= INQUIRY_ENTRY_AGE_MAX) {
@@ -7247,6 +7255,7 @@ static int hci_acl_create_conn_sync(struct hci_dev *hdev, void *data)
 
 		memcpy(conn->dev_class, ie->data.dev_class, 3);
 	}
+	hci_dev_unlock(hdev);
 
 	cp.pkt_type = cpu_to_le16(conn->pkt_type);
 	if (lmp_rswitch_capable(hdev) && !(hdev->link_mode & HCI_LM_MASTER))
-- 
2.43.0