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: Re: [PATCH] tty: vt: check for atomic context in con_write()
Date: Mon, 22 Jan 2024 23:08:29 +0900 [thread overview]
Message-ID: <7dc23b9d-5120-4966-b47b-fcabe270d498@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <82aa07d4-13ac-4b1d-80cd-0970c71752a5@kernel.org>
On 2024/01/22 15:48, Jiri Slaby wrote:
> On 20. 01. 24, 11:34, Tetsuo Handa wrote:
>> syzbot is reporting sleep in atomic context, for gsmld_write() is calling
>> con_write() with spinlock held and IRQs disabled.
>
> gsm should never be bound to a console in the first place.
>
> Noone has sent a patch to deny that yet.
>
> Follow:
> https://lore.kernel.org/all/49453ebd-b321-4f34-a1a5-d828d8881010@kernel.org/
>
> And feel free to patch that ;).
>
> thanks,
OK. Here is a deny-listing based filter using device number of sysfs entry.
(We don't want to compare with the function address of con_write().
Thus, this patch is comparing with device major/minor numbers.)
----------
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 4036566febcb..6f9730dce5aa 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3630,6 +3630,10 @@ static int gsmld_open(struct tty_struct *tty)
if (tty->ops->write == NULL)
return -EINVAL;
+ /* Can't be attached to virtual consoles. */
+ if (tty->dev && MAJOR(tty->dev->devt) == 4 && MINOR(tty->dev->devt) < 64)
+ return -EINVAL;
+
/* Attach our ldisc data */
gsm = gsm_alloc_mux();
if (gsm == NULL)
----------
Is it possible to use allow-listing based filtering?
(Attaching on /dev/tty (major=5, minor=0) causes current ssh session
to be closed. Unexpectedly loosing connection might be a problem for
fuzz testing...)
----------
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/tty.h>
int main(int argc, char *argv[]) {
int ldisc = N_GSM0710;
return ioctl(open(argv[1], O_RDWR | O_NOCTTY | O_NDELAY), TIOCSETD, &ldisc) == 0;
}
----------
next prev parent reply other threads:[~2024-01-22 14:08 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 [this message]
2024-01-24 10:06 ` [PATCH] tty: n_gsm: restrict tty devices to attach Tetsuo Handa
2024-01-24 13:14 ` 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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