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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Peilin Ye <yepeilin.cs@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        syzbot+24ebd650e20bd263ca01@syzkaller.appspotmail.com
Subject: [PATCH 4.19 091/346] Bluetooth: Fix slab-out-of-bounds read in hci_le_direct_adv_report_evt()
Date:   Mon, 28 Dec 2020 13:46:50 +0100
Message-Id: <20201228124924.200468197@linuxfoundation.org>
In-Reply-To: <20201228124919.745526410@linuxfoundation.org>
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From: Peilin Ye <yepeilin.cs@gmail.com>

commit f7e0e8b2f1b0a09b527885babda3e912ba820798 upstream.

`num_reports` is not being properly checked. A malformed event packet with
a large `num_reports` number makes hci_le_direct_adv_report_evt() read out
of bounds. Fix it.

Cc: stable@vger.kernel.org
Fixes: 2f010b55884e ("Bluetooth: Add support for handling LE Direct Advertising Report events")
Reported-and-tested-by: syzbot+24ebd650e20bd263ca01@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=24ebd650e20bd263ca01
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/bluetooth/hci_event.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5596,21 +5596,19 @@ static void hci_le_direct_adv_report_evt
 					 struct sk_buff *skb)
 {
 	u8 num_reports = skb->data[0];
-	void *ptr = &skb->data[1];
+	struct hci_ev_le_direct_adv_info *ev = (void *)&skb->data[1];
 
-	hci_dev_lock(hdev);
+	if (!num_reports || skb->len < num_reports * sizeof(*ev) + 1)
+		return;
 
-	while (num_reports--) {
-		struct hci_ev_le_direct_adv_info *ev = ptr;
+	hci_dev_lock(hdev);
 
+	for (; num_reports; num_reports--, ev++)
 		process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
 				   ev->bdaddr_type, &ev->direct_addr,
 				   ev->direct_addr_type, ev->rssi, NULL, 0,
 				   false);
 
-		ptr += sizeof(*ev);
-	}
-
 	hci_dev_unlock(hdev);
 }