linux-kernel - [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete

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Date:   Sat, 29 Aug 2020 18:11:12 +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 deref in hci_phy_link_complete_evt

Fix null pointer deref in hci_phy_link_complete_evt, there was no checking there for
the hcon->amp_mgr->l2cap_conn->hconn, and also in hci_cmd_work, for
hdev->sent_cmd. 

To fix this issue Add pointer checking in hci_cmd_work and
hci_phy_link_complete_evt.
[Linux-next-20200827]

Reported-by: syzbot+0bef568258653cff272f@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
Signed-off-by: Anmol Karn <anmol.karan123@...il.com>
---
 net/bluetooth/hci_core.c  | 4 ++++
 net/bluetooth/hci_event.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 68bfe57b6625..533048d2a624 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4922,6 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
 
 		kfree_skb(hdev->sent_cmd);
 
+		if(hdev->sent_cmd) {
+			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
+		}
+
 		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
 		if (hdev->sent_cmd) {
 			if (hci_req_status_pend(hdev))
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 4b7fc430793c..c621c8a20ea4 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
 		hci_dev_unlock(hdev);
 		return;
 	}
+	if(!(hcon->amp_mgr->l2cap_conn->hcon)) {
+		hci_dev_unlock(hdev);
+		return;
+	}
 
 	bredr_hcon = hcon->amp_mgr->l2cap_conn->hcon;
 
-- 
2.28.0