linux-kernel - Re: [PATCH] Bluetooth: hci_conn: fix potential double free in le_scan

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Message-ID: <081b216e6496e8cc2284df191dcc2d8b604d04f7.camel@redhat.com>
Date:   Thu, 26 May 2022 13:24:32 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Jianglei Nie <niejianglei2021@....com>, marcel@...tmann.org,
        johan.hedberg@...il.com, luiz.dentz@...il.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org
Cc:     linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: hci_conn: fix potential double free in
 le_scan_cleanup()

On Thu, 2022-05-26 at 17:49 +0800, Jianglei Nie wrote:
> When "c == conn" is true, hci_conn_cleanup() is called. The
> hci_conn_cleanup() calls hci_dev_put() and hci_conn_put() in
> its function implementation. hci_dev_put() and hci_conn_put()
> will free the relevant resource if the reference count reaches
> zero, which may lead to a double free when hci_dev_put() and
> hci_conn_put() are called again.
> 
> We should add a return to this function after hci_conn_cleanup()
> is called.
> 
> Signed-off-by: Jianglei Nie <niejianglei2021@....com>
> ---
>  net/bluetooth/hci_conn.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index fe803bee419a..7b3e91eb9fa3 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -166,6 +166,7 @@ static void le_scan_cleanup(struct work_struct *work)
>  	if (c == conn) {
>  		hci_connect_le_scan_cleanup(conn);
>  		hci_conn_cleanup(conn);
> +		return;

This looks not correct. At very least you should release the
hci_dev_lock.

Cheers,

Paolo