netdev - [Linux-kernel-mentees] [PATCH net v2] Bluetooth: Fix slab-out-of-bounds read in hci_le_direct_adv_report

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Date:   Wed,  9 Sep 2020 03:17:00 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>
Cc:     Peilin Ye <yepeilin.cs@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: [Linux-kernel-mentees] [PATCH net v2] Bluetooth: Fix slab-out-of-bounds read in hci_le_direct_adv_report_evt()

`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@...r.kernel.org
Fixes: 2f010b55884e ("Bluetooth: Add support for handling LE Direct Advertising Report events")
Reported-and-tested-by: syzbot+24ebd650e20bd263ca01@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=24ebd650e20bd263ca01
Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
---
Change in v2:
    - add "Cc: stable@" tag.

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

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 4b7fc430793c..aec43ae488d1 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5863,21 +5863,19 @@ static void hci_le_direct_adv_report_evt(struct hci_dev *hdev,
 					 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);
 }
 
-- 
2.25.1