[PATCH 4.19 123/346] Bluetooth: Fix null pointer dereference in hci_event_packet()

[Greg Kroah-Hartman]

From: Anmol Karn <anmol.karan123@xxxxxxxxx>

[ Upstream commit 6dfccd13db2ff2b709ef60a50163925d477549aa ]

AMP_MGR is getting derefernced in hci_phy_link_complete_evt(), when called
from hci_event_packet() and there is a possibility, that hcon->amp_mgr may
not be found when accessing after initialization of hcon.

- net/bluetooth/hci_event.c:4945
The bug seems to get triggered in this line:

bredr_hcon = hcon->amp_mgr->l2cap_conn->hcon;

Fix it by adding a NULL check for the hcon->amp_mgr before checking the ev-status.

Fixes: d5e911928bd8 ("Bluetooth: AMP: Process Physical Link Complete evt")
Reported-and-tested-by: syzbot+0bef568258653cff272f@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f
Signed-off-by: Anmol Karn <anmol.karan123@xxxxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/bluetooth/hci_event.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 622898d018f63..b58afd2d5ebf4 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4672,6 +4672,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
 		return;
 	}
 
+	if (!hcon->amp_mgr) {
+		hci_dev_unlock(hdev);
+		return;
+	}
+
 	if (ev->status) {
 		hci_conn_del(hcon);
 		hci_dev_unlock(hdev);
-- 
2.27.0