Merge: CVE-2024-36011: Bluetooth: HCI: Fix potential null-ptr-deref

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5012

JIRA: https://issues.redhat.com/browse/RHEL-38466
CVE: CVE-2024-36011

```
Bluetooth: HCI: Fix potential null-ptr-deref

Fix potential null-ptr-deref in hci_le_big_sync_established_evt().

Fixes: f777d88 (Bluetooth: ISO: Notify user space about failed bis connections)
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
(cherry picked from commit d270600)
```

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

Approved-by: Bastien Nocera <bnocera@redhat.com>
Approved-by: David Marlin <dmarlin@redhat.com>
Approved-by: Tony Camuso <tcamuso@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Rado Vrbovsky <rvrbovsk@redhat.com>

Author: emmil

net/bluetooth/hci_event.c

@@ -6900,6 +6900,8 @@ static void hci_le_big_sync_established_evt(struct hci_dev *hdev, void *data,
 			u16 handle = le16_to_cpu(ev->bis[i]);
 
 			bis = hci_conn_hash_lookup_handle(hdev, handle);
+			if (!bis)
+				continue;
 
 			set_bit(HCI_CONN_BIG_SYNC_FAILED, &bis->flags);
 			hci_connect_cfm(bis, ev->status);