From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Jiri Slaby <jirislaby@kernel.org>,
syzbot <syzbot+06fa1063cca8163ea541@syzkaller.appspotmail.com>,
syzkaller-bugs@googlegroups.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Starke, Daniel" <daniel.starke@siemens.com>,
Lee Jones <lee@kernel.org>, Fedor Pchelkin <pchelkin@ispras.ru>
Cc: linux-kernel@vger.kernel.org,
linux-serial <linux-serial@vger.kernel.org>
Subject: [PATCH] tty: n_gsm: restrict tty devices to attach
Date: Wed, 24 Jan 2024 19:06:04 +0900 [thread overview]
Message-ID: <42d17017-1d30-4c54-9c28-9d9ba2494e07@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <7dc23b9d-5120-4966-b47b-fcabe270d498@I-love.SAKURA.ne.jp>
syzbot is reporting sleep in atomic context, for gsmld_write() is calling
con_write() with spinlock held and IRQs disabled.
Since n_gsm is designed to be used for serial port, reject attaching to
virtual consoles and PTY devices, by checking tty's device major/minor
numbers at gsmld_open().
Link: https://www.kernel.org/doc/html/v6.7/driver-api/tty/n_gsm.html
Reported-by: syzbot+06fa1063cca8163ea541@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=06fa1063cca8163ea541
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
drivers/tty/n_gsm.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 4036566febcb..14581483af78 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3623,6 +3623,7 @@ static void gsmld_close(struct tty_struct *tty)
static int gsmld_open(struct tty_struct *tty)
{
struct gsm_mux *gsm;
+ int major;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
@@ -3630,6 +3631,17 @@ static int gsmld_open(struct tty_struct *tty)
if (tty->ops->write == NULL)
return -EINVAL;
+ major = tty->driver->major;
+ /* Reject Virtual consoles */
+ if (major == 4 && tty->driver->minor_start == 1)
+ return -EINVAL;
+ /* Reject Unix98 PTY masters/slaves */
+ if (major >= 128 && major <= 143)
+ return -EINVAL;
+ /* Reject BSD PTY masters/slaves */
+ if (major >= 2 && major <= 3)
+ return -EINVAL;
+
/* Attach our ldisc data */
gsm = gsm_alloc_mux();
if (gsm == NULL)
--
2.18.4
next prev parent reply other threads:[~2024-01-24 10:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-18 9:51 [syzbot] [dri?] BUG: scheduling while atomic in drm_atomic_helper_wait_for_flip_done syzbot
2024-01-18 14:18 ` Tetsuo Handa
2024-01-20 10:34 ` [PATCH] tty: vt: check for atomic context in con_write() Tetsuo Handa
2024-01-21 3:48 ` Hillf Danton
2024-01-21 11:34 ` Tetsuo Handa
2024-01-22 6:48 ` Jiri Slaby
2024-01-22 14:08 ` Tetsuo Handa
2024-01-24 10:06 ` Tetsuo Handa [this message]
2024-01-24 13:14 ` [PATCH] tty: n_gsm: restrict tty devices to attach Greg Kroah-Hartman
2024-02-03 13:45 ` Tetsuo Handa
2024-02-06 14:28 ` Greg Kroah-Hartman
2024-04-20 11:17 ` [syzbot] [dri?] BUG: scheduling while atomic in drm_atomic_helper_wait_for_flip_done Tetsuo Handa
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