Commit 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple
hcon") reintroduces a previously fixed bug [1] ("KASAN: slab-use-after-free
Read in hci_conn_hash_flush"). This bug was originally fixed by commit
5dc7d23e167e ("Bluetooth: hci_conn: Fix possible UAF").
The hci_conn_unlink function was added to avoid invalidating the link
traversal caused by successive hci_conn_del operations releasing extra
connections. However, currently hci_conn_unlink itself also releases extra
connections, resulted in the reintroduced bug.
This patch follows a more robust solution for cleaning up all connections,
by repeatedly removing the first connection until there are none left. This
approach does not rely on the inner workings of hci_conn_del and ensures
proper cleanup of all connections.
However, we need to make sure that hci_conn_del never fails. Indeed it
doesn't, as it now always returns zero. To make this a bit clearer, this
patch also changes its return type to void.
Reported-by: syzbot+8bb72f86fc823817bc5d@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=8bb72f86fc823817bc5d
Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@xxxxxxxxxx>
---
include/net/bluetooth/hci_core.h | 2 +-
net/bluetooth/hci_conn.c | 28 ++++++++++++----------------
2 files changed, 13 insertions(+), 17 deletions(-)
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index a6c8aee2f..8baf34639 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1327,7 +1327,7 @@ int hci_le_create_cis(struct hci_conn *conn);
struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
u8 role);
-int hci_conn_del(struct hci_conn *conn);
+void hci_conn_del(struct hci_conn *conn);
void hci_conn_hash_flush(struct hci_dev *hdev);
void hci_conn_check_pending(struct hci_dev *hdev);
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 640b951bf..85c34c837 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1109,7 +1109,7 @@ static void hci_conn_unlink(struct hci_conn *conn)
hci_conn_del(conn);
}
-int hci_conn_del(struct hci_conn *conn)
+void hci_conn_del(struct hci_conn *conn)
{
struct hci_dev *hdev = conn->hdev;
@@ -1160,8 +1160,6 @@ int hci_conn_del(struct hci_conn *conn)
* rest of hci_conn_del.
*/
hci_conn_cleanup(conn);
-
- return 0;
}
struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t src_type)
@@ -2462,22 +2460,20 @@ void hci_conn_enter_active_mode(struct hci_conn *conn, __u8 force_active)
/* Drop all connection on the device */
void hci_conn_hash_flush(struct hci_dev *hdev)
{
- struct hci_conn_hash *h = &hdev->conn_hash;
- struct hci_conn *c, *n;
+ struct list_head *head = &hdev->conn_hash.list;
+ struct hci_conn *conn;
BT_DBG("hdev %s", hdev->name);
- list_for_each_entry_safe(c, n, &h->list, list) {
- c->state = BT_CLOSED;
-
- hci_disconn_cfm(c, HCI_ERROR_LOCAL_HOST_TERM);
-
- /* Unlink before deleting otherwise it is possible that
- * hci_conn_del removes the link which may cause the list to
- * contain items already freed.
- */
- hci_conn_unlink(c);
- hci_conn_del(c);
+ /* We should not traverse the list here, because hci_conn_del
+ * can remove extra links, which may cause the link traversal
+ * to hit items that have already been released.
+ */
+ while ((conn = list_first_entry_or_null(head,
+ struct hci_conn, list)) != NULL) {
+ conn->state = BT_CLOSED;
+ hci_disconn_cfm(conn, HCI_ERROR_LOCAL_HOST_TERM);
+ hci_conn_del(conn);
}
}
--
2.40.0
