Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer dereference in hci_event_packet()

[Dan Carpenter]

On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote:
> Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr'
> as NULL. Fix it by adding pointer check for it.
> 
> Reported-and-tested-by: syzbot+0bef568258653cff272f@xxxxxxxxxxxxxxxxxxxxxxxxx
> Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f
> Signed-off-by: Anmol Karn <anmol.karan123@xxxxxxxxx>
> ---
>  net/bluetooth/hci_event.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 4b7fc430793c..871e16804433 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
>  		return;
>  	}
>  
> +	if (IS_ERR_OR_NULL(hcon->amp_mgr)) {

It can't be an error pointer.  Shouldn't we call hci_conn_del() on this
path?  Try to find the Fixes tag to explain how this bug was introduced.

(Don't rush to send a v2.  The patch requires quite a bit more digging
and detective work before it is ready).

> +		hci_dev_unlock(hdev);
> +		return;
> +	}
> +
>  	if (ev->status) {
>  		hci_conn_del(hcon);
>  		hci_dev_unlock(hdev);

regards,
dan carpenter