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

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Message-ID: <2023100507-worst-quarrel-2b97@gregkh>
Date:   Thu, 5 Oct 2023 13:55:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Lee Jones <lee@...nel.org>
Cc:     "Starke, Daniel" <daniel.starke@...mens.com>,
        "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

On Thu, Oct 05, 2023 at 12:46:32PM +0100, Lee Jones wrote:
> On Thu, 05 Oct 2023, Starke, Daniel wrote:
> 
> > > > 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" :(
> 
> Ah, you mean there are others that we need to consider?
> 
> I was just covering off con_write() from drivers/tty/vt/vt.c.
> 
> Does anyone have a counter proposal?

consoles are dynamically assigned, the device knows if it is a console
or not, so there is a way to determine this at runtime.  It's not a
device naming thing at all.

thanks,

greg k-h