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

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Date:   Mon, 9 Nov 2020 13:16:53 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Peilin Ye <yepeilin.cs@...il.com>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net v2] Bluetooth: Fix
 slab-out-of-bounds read in hci_le_direct_adv_report_evt()

Hi Peilin,

> `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);
> }

patch has been applied to bluetooth-next tree.

Regards

Marcel