linux-kernel - [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer dereference in hci_event

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Date:   Tue, 29 Sep 2020 23:02:31 +0530
From:   Anmol Karn <anmol.karan123@...il.com>
To:     marcel@...tmann.org, johan.hedberg@...il.com
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        netdev@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        kuba@...nel.org, davem@...emloft.net, anmol.karan123@...il.com,
        syzbot+0bef568258653cff272f@...kaller.appspotmail.com
Subject: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer dereference in hci_event_packet()

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@...kaller.appspotmail.com 
Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f 
Signed-off-by: Anmol Karn <anmol.karan123@...il.com>
---
Cahnge in v2:
  - Replaced IS_ERR_OR_NULL check with NULL check only (Suggested by: Dan Carpenter <dan.carpenter@...cle.com>)
  - Added "Fixes:" tag (Suggested by: Dan Carpenter <dan.carpenter@...cle.com>)


 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 4b7fc430793c..b084142c578e 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
 		return;
 	}
 
+	if (!hcon->amp_mgr) {
+		hci_dev_unlock(hdev);
+		return 0;
+	}
+
 	if (ev->status) {
 		hci_conn_del(hcon);
 		hci_dev_unlock(hdev);
-- 
2.28.0