[SRU Bionic/Focal/OEM-5.10/OEM-5.14/Hirsute/Impish/Unstable] Bluetooth: hci_ldisc: require CAP_NET_ADMIN to attach N_HCI ldisc

[Thadeu Lima de Souza Cascardo]

BugLink: https://bugs.launchpad.net/bugs/1949516

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 at canonical.com>
Signed-off-by: Marcel Holtmann <marcel at holtmann.org>
(cherry picked from commit c05731d0c6bd9a625e27ea5c5157ebf1303229e0)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.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
 	 */
-- 
2.32.0