linux-kernel - Re: [PATCH next] Bluetooth: L2CAP: Fix NULL dereference in l2cap_recv

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Message-ID: <CABBYNZK-ibR-+ri_+FFiorLkEvT_1tD2YKSOeSuTsyoS4dM1CA@mail.gmail.com>
Date: Wed, 12 Feb 2025 17:23:42 -0500
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Luiz Augusto von Dentz <luiz.von.dentz@...el.com>, Marcel Holtmann <marcel@...tmann.org>, 
	Johan Hedberg <johan.hedberg@...il.com>, linux-bluetooth@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH next] Bluetooth: L2CAP: Fix NULL dereference in l2cap_recv_acldata()

Hi Dan,

On Wed, Feb 12, 2025 at 11:40 AM Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> The "conn" pointer is NULL so this "goto drop;" will lead to a NULL
> dereference when we call mutex_unlock(&conn->lock). Free the skb and
> return directly instead.
>
> Fixes: dd6367916d2d ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  net/bluetooth/l2cap_core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 6cdc1dc3a7f9..fec11e576f31 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -7456,8 +7456,10 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
>
>         hci_dev_unlock(hcon->hdev);
>
> -       if (!conn)
> -               goto drop;
> +       if (!conn) {
> +               kfree_skb(skb);
> +               return;
> +       }
>
>         BT_DBG("conn %p len %u flags 0x%x", conn, skb->len, flags);
>
> --
> 2.47.2

I went ahead and fixed this in place since it has not been sent to net
yet, I did add your Signed-off-by though.

-- 
Luiz Augusto von Dentz