linux-kernel - [PATCH] tty: n_gsm: require CAP_NET_ADMIN to attach N

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Date:   Mon, 31 Jul 2023 15:59:42 -0300
From:   Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
To:     linux-serial@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Subject: [PATCH] tty: n_gsm: require CAP_NET_ADMIN to attach N_GSM0710 ldisc

Any unprivileged user can attach N_GSM0710 ldisc, but it requires
CAP_NET_ADMIN to create a GSM network anyway.

Require initial namespace CAP_NET_ADMIN to do that.

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

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 1cdefac4dd1b..c7a787f10a9c 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3576,6 +3576,9 @@ static int gsmld_open(struct tty_struct *tty)
 {
 	struct gsm_mux *gsm;
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	if (tty->ops->write == NULL)
 		return -EINVAL;
 
-- 
2.34.1