linux-kernel - [PATCH] Bluetooth: hci_ldisc: require CAP_NET_ADMIN to attach N

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Message-Id: <20210922115656.97723-1-cascardo@canonical.com>
Date:   Wed, 22 Sep 2021 08:56:56 -0300
From:   Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
To:     linux-bluetooth@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH] Bluetooth: hci_ldisc: require CAP_NET_ADMIN to attach N_HCI ldisc

Any unprivileged user can attach N_HCI ldisc and send packets coming from a
virtual controller by using PTYs.

Require initial namespace CAP_NET_ADMIN to do that.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
---
 drivers/bluetooth/hci_ldisc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 5ed2cfa7da1d..5e32e4d5367a 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -479,6 +479,9 @@ static int hci_uart_tty_open(struct tty_struct *tty)
 
 	BT_DBG("tty %p", tty);
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	/* Error if the tty has no write op instead of leaving an exploitable
 	 * hole
 	 */
-- 
2.30.2