[PATCH v2 net-next] Bluetooth: hci_conn: fix potential UAF in create_big_sync

[David Carlier <devnexen@gmail.com>]

Add hci_conn_valid() check in create_big_sync() to detect stale
connections before proceeding with BIG creation. Fix
create_big_complete() to handle the resulting -ECANCELED error
and validate the connection under hci_dev_lock() before
dereferencing, following the established pattern used by
create_le_conn_complete() and create_pa_complete().

Without this, create_big_complete() would unconditionally
dereference the stale conn pointer on error, causing a
use-after-free via hci_connect_cfm() and hci_conn_del().

Fixes: eca0ae4aea66 ("Bluetooth: Add initial implementation of BIS connections")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---

v1 -> v2: fix create_big_complete() to handle -ECANCELED and
  validate conn under hci_dev_lock(), matching the pattern in
  create_le_conn_complete() and create_pa_complete().
v1: https://lore.kernel.org/r/20260408155638.95927-1-devnexen@gmail.com
 net/bluetooth/hci_conn.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 11d3ad8d2551..feebe933efc8 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -2130,6 +2130,9 @@ static int create_big_sync(struct hci_dev *hdev, void *data)
 	u32 flags = 0;
 	int err;
 
+	if (!hci_conn_valid(hdev, conn))
+		return -ECANCELED;
+
 	if (qos->bcast.out.phys == BIT(1))
 		flags |= MGMT_ADV_FLAG_SEC_2M;
 
@@ -2204,11 +2207,22 @@ static void create_big_complete(struct hci_dev *hdev, void *data, int err)
 
 	bt_dev_dbg(hdev, "conn %p", conn);
 
+	if (err == -ECANCELED)
+		return;
+
+	hci_dev_lock(hdev);
+
+	if (!hci_conn_valid(hdev, conn))
+		goto done;
+
 	if (err) {
 		bt_dev_err(hdev, "Unable to create BIG: %d", err);
 		hci_connect_cfm(conn, err);
 		hci_conn_del(conn);
 	}
+
+done:
+	hci_dev_unlock(hdev);
 }
 
 struct hci_conn *hci_bind_bis(struct hci_dev *hdev, bdaddr_t *dst, __u8 sid,
-- 
2.53.0