Re: Crash when specifying non-existent serial port in speakup / tty_kopen

[Matthias Reichl]

On Wed, Nov 04, 2020 at 10:30:05PM +0100, Samuel Thibault wrote:
> 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?

Thanks a lot, good catch! This is indeed where the crash happens
and checking for tty->port in release_tty() prevents that.
I'll send a patch.

so long,

Hias