linux-kernel - Re: [PATCH] net/bluetooth: Fix bound check in event handling

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Message-Id: <8F6AC5BF-F50B-4C30-A73B-98526AF181EB@holtmann.org>
Date:   Sat, 2 Mar 2019 17:46:49 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Tomas Bortoli <tomasbortoli@...il.com>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        "open list:BLUETOOTH DRIVERS" <linux-bluetooth@...r.kernel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller@...glegroups.com
Subject: Re: [PATCH] net/bluetooth: Fix bound check in event handling

Hi Tomas,

> hci_inquiry_result_with_rssi_evt() can perform out of bound reads
> on skb->data as a bound check is missing.
> 
> Signed-off-by: Tomas Bortoli <tomasbortoli@...il.com>
> Reported-by: syzbot+cec7a50c412a2c03f8f5@...kaller.appspotmail.com
> Reported-by: syzbot+660883c56e2fa65d4497@...kaller.appspotmail.com
> ---
> Syzkaler reports:
> https://syzkaller.appspot.com/bug?id=d708485af9edc3af35f3b4d554e827c6c8bf6b0f
> https://syzkaller.appspot.com/bug?id=3acd1155d48a5acc5d76711568b04926945a6885
> 
> net/bluetooth/hci_event.c | 4 ++++
> 1 file changed, 4 insertions(+)
> 
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index ac2826ce162b..aa953d23bb72 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -3983,6 +3983,10 @@ static void hci_inquiry_result_with_rssi_evt(struct hci_dev *hdev,
> 		for (; num_rsp; num_rsp--, info++) {
> 			u32 flags;
> 
> +			if ((void *)(info + sizeof(info)) >
> +			   (void *)(skb->data + skb->len))
> +				break;
> +

first of all, the loop exists twice here. If one is vulnerable, then the second is a well. And second, can we not just do this inside the for-condition check or a lot simpler than this void casting fun.

Regards

Marcel