linux-kernel - RE: [PATCH 1/1] tty: n_gsm: Avoid sleeping during .write() whilst atomic

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Message-ID: <DB9PR10MB5881E8D3903C19EBAD9AF895E0CAA@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM>
Date:   Thu, 5 Oct 2023 11:38:27 +0000
From:   "Starke, Daniel" <daniel.starke@...mens.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lee Jones <lee@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Fedor Pchelkin <pchelkin@...ras.ru>,
        Jiri Slaby <jirislaby@...nel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "syzbot+5f47a8cea6a12b77a876@...kaller.appspotmail.com" 
        <syzbot+5f47a8cea6a12b77a876@...kaller.appspotmail.com>
Subject: RE: [PATCH 1/1] tty: n_gsm: Avoid sleeping during .write() whilst
 atomic

> > Would something like this tick that box?
> > 
> > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 
> > 1f3aba607cd51..5c1d2fcd5d9e2 100644
> > --- a/drivers/tty/n_gsm.c
> > +++ b/drivers/tty/n_gsm.c
> > @@ -3716,6 +3716,10 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
> >         if (!gsm)
> >                 return -ENODEV;
> >  
> > +       /* The GSM line discipline does not support binding to console */
> > +       if (strncmp(tty->name, "tty", 3))
> > +               return -EINVAL;
> 
> No, that's not going to work, some consoles do not start with "tty" :(

Also, I would recommend exiting as early as possible. E.g. in gsmld_open().
And please retain support for real serial devices (e.g. ttyS, ttyUSB,
ttyACM, ...).

Best regards,
Daniel Starke