linux-kernel - Re: [PATCH v2] tty: Fix WARNING in tty_set

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Date:   Fri, 1 Feb 2019 16:20:35 -0700
From:   shuah <shuah@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com,
        viro@...iv.linux.org.uk, gregkh@...uxfoundation.org,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        shuah <shuah@...nel.org>
Subject: Re: [PATCH v2] tty: Fix WARNING in tty_set_termios()

On 2/1/19 2:28 AM, Johan Hovold wrote:
> On Thu, Jan 31, 2019 at 04:23:59PM -0700, Shuah Khan wrote:
>> tty_set_termios() has the following WARN_ON which can be triggered with a
>> syscall to invoke TIOCSETD __NR_ioctl.
> 
> That's the only way to set the hci line discipline. And it's the
> consequent ioctl that sets the uart protocol that triggers the warning,
> but only if the tty is a pty master, as I mentioned before.
> 
>> WARN_ON(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
>>                  tty->driver->subtype == PTY_TYPE_MASTER);
>> Reference: https://syzkaller.appspot.com/bug?id=2410d22f1d8e5984217329dd0884b01d99e3e48d
>>
>> The problem started with commit 7721383f4199 ("Bluetooth: hci_uart: Support
>> operational speed during setup") which introduced a new way for how
>> tty_set_termios() could end up being called for a master pty.
> 
> Please always include reviewers on CC, and especially if you end up
> citing them directly as you do here. Perhaps add quotation marks or at
> least a reference to the discussion where this solution was suggested.
> 

Thanks for the feedback. I am folding in your and Marcel's input in my
v3.

thanks,
-- Shuah