linux-kernel - Re: Crash when specifying non-existent serial port in speakup / tty

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Message-ID: <20201104213005.khivjvcwkaz7kz4g@function>
Date:   Wed, 4 Nov 2020 22:30:05 +0100
From:   Samuel Thibault <samuel.thibault@...-lyon.org>
To:     Matthias Reichl <hias@...us.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, speakup@...ux-speakup.org,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Crash when specifying non-existent serial port in speakup /
 tty_kopen

Matthias Reichl, le mer. 04 nov. 2020 22:15:05 +0100, a ecrit:
> > This looks like only a warning, did it actually crash?
> 
> Yes, scroll down a bit, the null pointer oops followed almost
> immediately after that
> 
> [   49.979043] BUG: kernel NULL pointer dereference, address: 0000000000000090

Ah, [   50.102938]  tty_init_dev+0xb5/0x1d0

probably the trailing release_tty call that does

tty->port->itty = NULL;
(itty is after a struct tty_bufhead + the tty pointer, that looks
plausible).

so probably an if (tty->port) in release_tty could help?

Samuel